BLOOD AND BLOOD COMPONENT- introduction to blood physiology

BLOOD AND BLOOD
COMPONENTS
NUST 2016/2018/2019/2020-2021

LECTURE 3 : BLOOD AND BLOOD COMPONENTS
GENERAL PROPERTIES
FUNCTIONS
CONSTITUENTS OF WHOLE BLOOD
CONSTITUENTS OF PLASMA
FUNCTIONS OF THE PLASMA PROTEINS
RED BLOOD CELLS
MATURATION AND DESTRUCTION OF RBC
ERYTHROPOEISIS
FUNCTION OF RBC

•LECTURE 4
HEMOGLOBIN , ABNORMAL HB, HEMOBLOBINOPATHIES
WHITE BLOOD CELLS
PROPERTIES OF DIFFERENT TYPES OF WBC
MATURATION AND DESTRUCTION OF WBC: LYMPHOCYTES
•LECTURE 5
PLATELETS AND FUNCTION
HEMOSTASIS
CLOTTING MECHANISM(INTRINSIC & EXTRINSIC PATHWAYS)
CLOT RETRACTION AND FIBRINOLYSIS
HEMOPHILIA AND ANTICOAGULANTS

•LECTURE 6 : BLOOD GROUPS: AOB GROUPING
RHESUS BLOOD GROUPING AND ERYTHROBLASTOSIS
FOETALIS
BUFFERING PROPERTIES OF THE BLOOD
•LECTURE 7: IMMUNE FUNCTION AND NON SPECIFIC DEFENCES
INFLAMMATION
INFLAMMATORY RESPONSE
IMMUNE RESPONSE
•LECTURE 8: CELL MEDIATED IMMUNE RESPONSE
ANTIBODIES AND MECHANISMS OF ACTION OF ANTIBODIES
IMMUNOLOGICAL MEMORY
ALLERGY AND AUTOIMMUNE DISORDERS
LYMPH FUNCTION

•LESCTURE 3:
GENERAL PROPRRTIES
FUNCTIONS
CONSTITUENTS OF WHOLE BLOOD
CONSTITUENTS OF PLASMA
FUNCTION OF THE PLASMA PROTEINS
RED BLOOD CELLS
MATURATION AND DESTRUCTION OF RBC
ERYTHROPOEISIS
FUNCTION OF RBC

•3.I GENERAL PROPERTIES
3.2 FUNCTIONS AND COMPONENTS OF THE BLOOD
•Blood is the only liquid connective tissue. It comprises 8% of total body
weight (5 L in a normal adult).
•It plays a major role in the circulation system, that is the transport system
that supplies oxygen and substances absorbed from the GIT to the tissues,
returns CO
2to the lungs and other products of metabolism to the kidneys.
The functions of blood relate to its composition:
I.Transport:
#The blood transports dissolved gases, nutrients, waste products and
hormones.

#.The blood distributes nutrients absorbed at the digestive tract and
released from stores , adipose tissue or the liver.
# Transports hormones from glands to the target cells
# Absorbs and carries waste production to the kidneys for elimination
#Homeostatic: regulates body temperature, pH, hemostasis and fluid
exchange.

#II Regulation of the pH and ions composition
1.By diffusion between the interstitial fluid and the blood
The blood helps eliminate local differences or excess ions such as
calcium or potassium
2.Absorbs and metabolizes the acids generated by active tissues(lactic
acid produced by skeletal muscles)
# III Restriction of fluid loss at the site of injury
Enzymes and other substances in the blood respond to the breaks in
the vessel wall by initiating the process of coagulation

# IV Immunological:
Defense against bacteria, viruses and foreign bodies by leukocytes
Defense against toxins and pathogens
The blood produces and transports specialized cells (WBC) to the site
of infection and digests or removes debris.
•The blood delivers antibodies to attack invading agents or foreign
bodies.

3.3 CONSTITUENTS OF WHOLE BLOOD
Plasma (55%): a watery substance containing dissolved solutes and
proteins in suspension.
Cells and cellular fragments (45%):
●erythrocytes (99%), also know as red blood cells (RBCs)
●platelets (< 1%)
●leukocytes (< 1%) or white blood cells (WBCs).

PLASMA
Plasma comprises
Water : forms the medium of suspension and transport of proteins, solutes
and gases ,so influences partial pressures and gas exchange.
Water is important in temperature regulation because it releases heat.
It also removes waste and breakdown products.
Solutes:
electrolytes in particular create osmotic pressure. Ions, e.g. HCO3−, are
important in buffering pH change.
Proteins:
are important buffers and exert oncotic pressure:
Albumin:
particularly important for vascular oncotic pressure and fluid exchange.
It also transports fatty acids, lipid-soluble hormones and some drugs

•Electrophoresis-Definition
• Electro=Electric; phoresis= Migration;Carry
•accross.
•• A kind of separation technique based on the differential migration
features of charged molecules in an electric field.

•Principle:
–In an electrical field charged molecules and
•particles migrate to the opposite charge.
•–Usually in aqueous solution(Buffer).
•–Due to their varying charges and masses, different molecules and
particles in the mixture are migrate at different speeds.
•–As a result; separated into single fractions(bands).

•These different bands have a different zone with the characteristic presence of different
proteins. e.g.
•Albumin zone shows the only albumin.
•alpha1-zone shows :
•alpha1 –lipoprotein.
•High-density lipoprotein.
•alpha 1 -antitrypsin.
•alpha 2 zone shows :
•alpha 2 macroglobulins.
•Haptoglobin.
•β -lipoprotein.
•beta zone shows :
•Transferrin.
•Complement 3 (C3).
•gamma zone shows :
•Fibrinogen.
•IgA.
•IgM.
•IgG.

Globulins:
•α and β globulins transport hormones and iron, respectively.
•γ Globulins (antibodies) defend against viruses and bacteria.
•Other components: including fibrinogen, which is important in the
process of blood clotting.

3. 4. RED BLOOD CELLS
GENERAL PROPERTIES
ERYTHROPOEISIS
MATURATION AND DESTRUCTION OF RBC
FUNCTIONS OF RBC

•GENERAL PROPERTIES
•The major function of red blood cells( erythrocytes):contain
hemoglobin, which in turn carries oxygen from the lungs to the
tissues.
•In some lower animals, hemoglobincirculates as free protein in the
plasma, not enclosed in red blood cells.

•Whenitisfreeintheplasmaofthehumanbeing,about3percentof
itleaksthroughthecapillarymembraneintothetissuespacesor
throughtheglomerularmembraneofthekidneyintotheglomerular
filtrateeachtimethebloodpassesthroughthecapillaries.
•Forhemoglobintoremaininthehumanbloodstream,itmustexist
insideredbloodcells.

•ShapeandSizeofRedBloodCells.
•Normalshape:biconcavediscshavingameandiameterofabout7.8
micrometersandathicknessof2.5micrometersatthethickestpoint
and1micrometerorlessinthecenter.
•Theaveragevolumeoftheredbloodcellis90to95cubicmicrometers

•The shapes of red blood cells can change remarkably as the cells
squeeze through capillaries.
•The red blood cell is like a “bag” that can be deformed into almost
any shape.
•The normal cell has a great excess of cell membrane for the quantity
of material inside, deformation does not stretch the membrane
greatly and, consequently, does not rupture the cell, as would be the
case with many other cells.

•Concentration of Red Blood Cells in the Blood.
•In normal men: 5,200,000 (±300,000)/ cubic millimeter
•In normal women, it is 4,700,000 (±300,000).
•Persons living at high altitudes have greater numbers of red blood
cells.

Quantity of Hemoglobinin the Cells.
•Red blood cells can concentrate hemoglobinin the cell fluid up to about
34 grams in each 100 millilitersof cells
•This concentration does not rise above this value, because this is the
metabolic limit of the cell’s hemoglobin-forming mechanism.
•In normal people, the percentage of hemoglobinis almost always near the
maximum in each cell.
•However, when hemoglobinformation is deficient, the percentage of
hemoglobinin the cells may fall considerably below this value, and the
volume of the red cell may also decrease because of diminished
hemoglobinto fill the cell.

•Hematocrit(thepercentageofbloodcells):40to45percent
•Whenthehaematocritandthequantityofhemoglobinineach
respectivecellarenormal,thewholebloodofmencontainsan
averageof15gramsofhemoglobinper100millilitersofcells;for
women,itcontainsanaverageof14gramsper100milliliters.
•Eachgramofpurehemoglobiniscapableofcombiningwith1.34
millilitersofoxygen.

•Therefore, in a normal man:
•a maximum of about 20 millilitersof oxygen can be carried in
combination with hemoglobinin each 100 millilitersof blood,
•and in a normal woman, 19 millilitersof oxygen can be carried.

•ERYTHROPOIESIS AND MATURATION
Theerythrocytesareunabletoreplenishtheirnumber.
SotheoldRBCmustbereplacedbynewcells.Theaveragenormalred
bloodcellscountis5.2million/microliterinmenand4.7million/microliter
infemale.
Theshortlifespan(120days)necessitatestheerythropoiesis,whichisthe
thedevelopment,thedifferentiationandthematurationofRBCsfrom
primitivestemcells
Ittakesplaceinthebonemarrow.

Intrauterine development
•First month : erythrocytes are produced in the yolk sac
•Third month of gestation : in the developing spleen
•At 7 months of gestation : exclusively in the bone marrow
•In children : all bones with red bone marrow, liver and spleen
•In adult: long bones like femur, humerus
• other bones :skull, sternum, vertebrae,rib,pelvis

Erythrocyte differentiation
The process/pathway through an erythrocyte matures from hemocytoblast
to full-blown erythrocyte
8 Stages
The 7 stages: In bone marrow then released in the bloodstream as
reticulocytewhich after 1-2 days
matures in erythrocyte
Stages :1. Hemocytoblast (pluripotent hematopoietic stem cell)
2.Common myeloid progenitor(Multipotentstem cell)
3. Unipotentstem cell
4. Pronormoblast
5. Basophilic normoblast(erythroblast)
6. Polynormatophilicnormoblast
7. Orthochromatic normoblast
8. Reticulocyte

•STEM CELLS
•These cells have extensive proliferative capacity and also the ability to give rise to
the news cells( cell renewal)(pluripotent hematopoietic stem cell)
•to differenciateinto any blood cells line(pluripotency)
•Hematopoietic stem Cells (HSGC) are bone marrow cells that have the capacity of
producing all types of cells
•They differenciateinto one or another type of committed stem (progenitor)

Regulation of erythropoiesis
Factors affecting erythropoiesis
1. General factors : hypoxia, growth inducers, vitamins
2.Maturation factors : Vitamin B12, folic acid
3. Factors necessary for Hemoglobin production
Vitamin c : helps Fe+++…Fe++
Proteins: Amino acids help in globin synthesis
Iron and copper : Heme synthesis
4.Growth inducers : Interleukins 1-3-6

The primary stimulus for erythrocyte production is low oxygen .
•Thelowoxygenlevelstimulatesthekidneystosecrete
erythropoietin(EPO)intothebloodwhichwillstimulatesthebone
marrowtoproduceerythrocytes.
•EPOactsonderivativesofundifferentiatedcellsthathavealready
committedtobecomingRBC’sstimulatingtheproliferationand
maturationintomatureRBC’s

ERYTHROPOIETIN (EPO)
•Is a glycoprotein MW 34000
•85% is formed in the kidney: peritubular capillaries of the renal
tubules of the kidney
•15% is formed in the liver: hepatic cells and Kupffers
•Breakdown occurs in the liver( half live : 5 hours)

•Erythropoietin stimulation
•Erythropoiesis can be indirectly stimulated by some hormones:
thyroxin, growth hormone, androgen(not estrogen)
•In the plasma
When peripheral tissues are exposed to hypoxia, anemia, reduced kidney
blood flow, altitude, respiratory surface is reduce( fibrosis), other lung
diseases.
(kidney hypoxia), EPO is released

•Functions of erythropoietin
•EPO increases the production of Red Blood cells(RBc) in 3
ways:
•1 Promote pronormoblastsproduction
•2.Shortens the transition time through the normoblastsstage
•3. Promotes the early release of reticulocytes

Maturation of RBC
•Maturation of RBCs requires : Vitamin B12(cyanocobalamin) and folic
acid
•There is continuing need to replenish RBCs : the erythropoietic cells of
the bone marrow are among the most rapidly growing and
reproducing cells in the entire body.
•Their maturation and rate of production are affected greatly by a
person’s nutritional status.

Two vitamins are important in the final maturation of RBcs:
vitamin B12 and folic acid
These vitamins are essential for the synthesis of DNA as required for the
formation of thymidine triphosphate, one of the essential building blocks
of DNA.

•Lack of either vitamin B12 or folic acid causes abnormal and diminished
DNA and, consequently, failure of nuclear maturation and cell division.
As result
The erythroblastic cells of the bone marrow, will fail to proliferate rapidly,
produce mainly larger than normal RBCs called macrocytes, and the cell
itself has a flimsy membrane and is often irregular, large, and oval instead
of the usual biconcave disk.

Vitamin B12 and maturation failure
Pernicious anemia
Cause :
poor absorption from the gastrointestinal tract
This is often occurs in the disease pernicious anemia, in which the basic
abnormality is an atrophic gastric mucosa that fails to produce
normal gastric secretions.
The parietal cells of the gastric glands secrete a glycoprotein called
intrinsic factor, which combines with vitamin B12 in food and makes
the B12 available for absorption by the gut

•Intrinsic factor binds tightly with the vitaminB12.In this bound state, the
B12 is protected from digestion by the gastrointestinal secretions
•Still in the bound state, intrinsic factor binds to specific receptor sites on
the brush border membranes of the mucosal cells in the ileum.
•Vitamin B12 is then transported into the blood during the next few hours
by the process of pinocytosis, carrying intrinsic factor and the vitamin
together through the membrane.

•Once vitamin B12 has been absorbed from the gastrointestinal tract,
it is first stored in large quantities in the liver and then is released
slowly as needed by the bone marrow.
•Minimum amount of vitamin B12 required each day to maintain
normal RBC maturation is only 1 to 3 micrograms, and the normal
storage in the liver and other body tissues is about 1000 times this
amount.
•It will require, 3 to 4 years of defective B12 absorption to cause
maturation failure anemia.

•Folic acid and maturation failure( Pteroylglumatic acid)
Folic acid is a normal constituent of green vegetables, some fruits, and meats
(especially liver).
However, it is easily destroyed during cooking.
People with gastrointestinal absorption abnormalities, such as the frequently
occurring small intestinal disease called sprue, often have serious difficulty
absorbing both folic acid and vitamin B12.
Therefore, in many instances of maturation failure, the cause is deficiency of
intestinal absorption of both folic acid and vitamin B12.

FUNCTIONS OF RBC
•Redbloodcells(RBCs),alsoknownaserythrocytes,arebyfarthe
mostabundantcellsintheblood.
•RBCsgiveblooditscharacteristicredcolor.
•RBCsaccountforapproximately40to45percentoftheblood.
•ThispercentageofbloodmadeupofRBCsisafrequentlymeasured
numberandiscalledthehematocrit.
•Theratioofcellsinnormalbloodis600RBCsforeachwhiteblood
celland40platelets.

•The primary function of red blood cells is to transport oxygen from
the lungs to the cells of the body.
•An RBC containshemoglobin, a molecule specially designed to hold
oxygen and carry it to cells that need it.
•Hemoglobin combines loosely with oxygen in the lungs, where the
oxygen level is high, and then easily releases it in the capillaries,
where the oxygen level is low.
•Each molecule of hemoglobin contains four iron atoms, and each iron
atom can bind with one molecule of oxygen for a total of four oxygen
molecules.

OtherfunctionsoftheRBCs
•Theycontainalargequantityofcarbonicanhydrase,anenzymethat
catalyzesthereversiblereactionbetweencarbondioxide(CO2)and
watertoformcarbonicacid(H2CO3),increasingtherateofthis
reactionseveralthousandfold.
•Therapidityofthisreactionmakesitpossibleforthewaterofthe
bloodtotransportenormousquantitiesofCO2intheformof
bicarbonateion(HCO3–)fromthetissuestothelungs,whereitis
reconvertedtoCO2andexpelledintotheatmosphereasabodywaste
product.

•Buffer
The hemoglobinin the cells is an excellent acid-base buffer (as is true
of most proteins), so that the red blood cells are responsible for most
of the acid-base buffering power of whole blood.

LECTURE 4: HEMOGLOBIN
ABNORMALITIES OF HB
HEMOGLOBINOPATHIES( SICLE CELL ANEMIA,THALASSEMIA)

HEMOBLOBIN
•Introduction
•Structure of the hemoglobin
•Types of hemoglobin

Introduction
Hemoglobin is a protein in RBC whose function is to transport oxygen
from lungs to the tissues and to carry carbon dioxide back to the lungs
Hemoglobin is present in blood at concentration of 13.5-18.0 in men
and 11.5-16.0 g in female

Structure/synthesis
Thereare5basicstepsintheformationofthehemoglobin
Synthesis
HBisacomplexquaternaryshape,madeofchainsofpolypeptides:
Twoalphachains
Twobetachains
Eachmadeofglobularprotein(globulins)subunitsthatareconnected
together

SYNTHESIS OF HEMOGLOBIN
Begins in the proerythroblasts and continues even into the reticulocyte
stage of the red blood cells.
Therefore, when reticulocytes leave the bone marrow and pass into the
blood stream, they continue to form minute quantities of hemoglobin
for another day or so until they become mature erythrocytes

•First, succinyl-CoA, formed in the Krebs metabolic cycle, binds with
glycine to form a pyrrole molecule.
•In turn, four pyrroles combine to form protoporphyrin IX, which then
combines with iron to form the hememolecule.
•Finally, each hememolecule combines with a long polypeptide chain,
a globin synthesized by ribosomes, forming a subunit of hemoglobin
called a hemoglobinchain
•Each chain has a molecular weight of about 16,000; four of these in
turn bind together loosely to form the whole hemoglobinmolecule.

•Thereareseveralslightvariationsinthedifferentsubunithemoglobin
chains,dependingontheaminoacidcompositionofthepolypeptide
portion.
•Thedifferenttypesofchainsaredesignatedalphachains,beta
chains,gammachains,anddeltachains.

f
1.HemoglobinA:isacombinationoftwoalphachainsandtwoofbeta
chains,itisthemostcommonformofhemoglobin(95-98%)inthe
adulthumanbeing.
2.HemoglobinA2:isacombinationoftwoalphachainsandtwoof
deltachains,itrepresents2-3%ofhemoglobinintheadulthuman
being.
3.HemoglobinF(fetusHb):isacombinationoftwoalphachainsand
twoofgammachains,alsoitfoundinnewbornsbloodofabout1%of
theirhemoglobin.

•Eachalpha-chainhas141aminoacids,
•andeachb-chainhas146.
Genesforthealpha-chainarefoundonchromosome16andthosefor
theb-chainonchromosome11.
Globinchainsaresynthesizedinthecytosoloferythrocytes.
Eachhemoglobinchainhasahemeprostheticgroupcontainingan
atomofiron,andbecausetherearefourhemoglobinchainsineach
hemoglobinmolecule,onefindsfourironatomsineachhemoglobin
molecule

Each of these can bind loosely with one molecule of oxygen, making a total
of four molecules of oxygen (or eight oxygen atoms) that can be transported
by each hemoglobinmolecule.
Thetypesofhemoglobinchainsinthehemoglobinmoleculedeterminethe
bindingaffinityofthehemoglobinforoxygen.Abnormalitiesofthechains
canalterthephysicalcharacteristicsofthehemoglobinmoleculeaswell.
•

•In sickle cell anemia, the amino acid valine is substituted for glutamic
acid at one point in each of the two beta chains. When this type of
hemoglobinis exposed to low oxygen, it forms elongated crystals inside
the red blood cells that are sometimes 15 micrometersin length.
These make it almost impossible for the cells to pass through many small
capillaries, and the spiked ends of the crystals are likely to rupture the cell
membranes, leading to sickle cell anemia.

Hemoglobin and oxygen affinity
HbF
•Life span 80 days
•Greater affinity for oxygen
HbA
•Life span 120 days
•Less affinity

•Oxygen-haemoglobin bond
Oxygen does not combine with the two positive bonds of the iron in the
hemoglobinmolecule.
It binds loosely with one of the so-called coordination bonds of the iron atom.
This is an extremely loose bond, so that the combination is easily reversible.
Moreover,theoxygen does not become ionic oxygen but is carried as molecular
oxygen (composed of two oxygen atoms) to the tissues, where, because of the
loose, readily reversible combination, it is released into the tissue fluids still in
the form of molecular oxygen rather than ionic oxygen.

•AFFINITY OF OXYGEN HbF vs HbA
Greater affinity of HbF oxygen vs HbA affinity
•1. composition of blood
•Adult : RBCs concentration ( hematocrit) : 35% normal in a pregnant
woman
Plasma : >50%
Rest : other cells
Fetal : RBCs concentration( hematocrit) : 55%
Plasma less
The higher concentration of RBCs(hematocrit) in fetal explains the greater
affinity for oxygen

Function of 2,3 DGP
Helps RBCs to get rid of oxygen
The ease with which haemoglobin releases oxygen to the tissues is controlled by erythrocytic
2,3-diphosphoglycerate (2,3-DPG) such that an increase in the concentration of 2,3-DPG
decreases oxygen affinity and vice versa.
In HbA
2,3 DPG binds to beta subunit of the hemoglobin . By doing so, it changes the conformation of the Hb,
causes it to readily release ( charges) oxygen …
In HbF
In HbF, 2,3 DGP does not bind to because the structure/the presence of
gamma subunit ( it repels the 2,3DGP), hence oxygen remains attached to Hb.
2,3 DGP is increased in situation of anemia, chronique lung diseases,altitude

•Normally in adult , the binding pocket for 2,3 DPG contains histidine
(positively charged)
•1 molecule of 2,3 BPG binds to a pocket formed by 2 beta-globulin
chains in the centre of the deoxyhemoglobintetramer.
•The pocket contains positively charged amnoacidsthat form the ionic
bonds with negatively charged phosphate group 2,3 BPG

•The fetal hemoglobin can bind oxygen at a much lower partial
pressure, because it obtain oxygen from the mother blood stream.

•In foetal, the positivehistidine residues of HbAβ-subunits that are
essential for forming the 2,3-BPG binding pocket are replaced by
serine (negatively charged)residues in HbFγ-subunits.
•Foetal hemoglobin(HbF) exhibits a low affinity for 2,3-BPG, resulting
in a higher binding affinity for oxygen.

•Normal adult hemoglobin molecules (HbA) has a molecular mass of 64 458 Da
with a complex quaternary structure
•Each erythrocyte contains around 200–300 million molecules of hemoglobin.
•Molecules of Hbaccount for 95% of intracellular proteins
•The hemoglobin(Hb) of whole blood is reported in gram of Hb/100 ml
•Normal (male):14-18 g/dl
(Female): 12-16 g/dl

Fetal Hemoglobin
The RBCs of an embryo
Fetal Hb(HbF) binds to oxygen more readily than does the Hbof an adult(HbA)
Developing foetuscan steal O
2from maternal bloodstream at the placenta
(better access to mother’s blood)
Birth to 6-12 months : foetalHbis converted to adult form of hemoglobin(HbA)
•Fetal haemoglobin(HbF) comprises two gamma-chains and two b-chains.
•At birth, 50–95% of a baby’s hemoglobin is HbF, but these levels decline after 6
months as more HbA is produced.
•In a healthy adult, 1% of hemoglobin is HbF.
•The oxygen affinity of HbF is substantially greater than HbA to facilitate the
transfer of oxygen between the maternal and fetal circulations in the placenta.

•Functions of haemoglobin
Hemoglobin has multiple functions:
Transport of oxygen from the lungs to the tissues, mostly to facilitate
oxidative phosphorylation in the mitochondria.
Carriage of carbon dioxide from tissues to the lungs as carbaminohemoglobin
Buffering of hydrogen ions formed in the erythrocyte from the conversion of
carbon dioxide into bicarbonate.
Nitric oxide metabolism.

Destruction of RBCs
When RBCs burst, haemoglobinis released. The haemoglobin is then phagocytized
almost immediately by macrophages in many parts of the body, but especially by
the Kupffer cells of the liver and macrophages of the spleen and bone marrow.
The macrophages release ironfrom the haemoglobin and pass it back into the
blood, to be carried by transferrin either
to the bone marrow for the production of new RBCs or
to the liver and other tissues for storage in the form of ferritin.
The porphyrin portion of the haemoglobin molecule is converted by the
macrophages, through a series of stages, into the bile pigment bilirubin, which is
released into the blood and later removed from the body by secretion through the
liver into the bile.

•Aged, damaged RBCs are destroyed in Liver, Spleen and Bone marrow.
•Hemoglobin → Heme+ Globin (this protein is then degraded to amino acids).
•Heme→ Biliverdin → Bilirubin → Urobilinogen → Stercobilin → excreted in feces.
•Bilirubin travels in blood complexed with albumin.
•Too much bilirubin in blood causes jaundice:thissituation is caused by increased
RBCs destruction, liver dysfunction, or bile duct obstruction.
•Liver esterifies bilirubin to bilirubin diglucuronide to make it more soluble, and
secretes it in bile. If bile duct obstructs, then bilirubin accumulates.
•Some urobilinogen is reabsorbed, transported to kidney, where it is converted to
urobilin, which gives urine its yellow color.
•Stercobilin gives feces their brown color.

•ANEMIAS
•Anemiaisdeficiencyofhaemoglobinintheblood.Itcanbecausedbyeither
toofewRBCsortoolittlehaemoglobininthecells.
Typesofanemia
a.Anemiaduetobloodloss
•Afterrapidhemorrhagethereislossofthefluidportionoftheplasmaand
RBCs.Thefluidportioncanbereplacedin1to3days,butthisresponse
resultsinalowconcentrationofRBCs.
RBCconcentrationusuallyreturnstonormalwithin3to6weeksifthereisnot
asecondhemorragicepisode
•Incasechronicbloodlossoccurs,apersonfrequentlycannotabsorbenough
ironfromtheintestinetoformhemoglobinasrapidlyasitislost.
RBCsthataremuchsmallerthannormalandhavetoolittlehemoglobininside
themarethenproduced,givingrisetomicrocytic,hypochromicanemia,

b.Anemiaduetobonemarrowmalfunction(aplasticanemia)
Aplasticanaemiadevelopsasaresultofbonemarrowdamage.
Bonemarrowaplasiameanslackoffunctioningbonemarrow.
Itcanbeabirthorcanresultfrom
1.Exposuretohigh-doseradiationorchemotherapyforcancertreatmentwhichcan
damagestemcellsofthebonemarrow,followedinafewweeksbyanemia.
2.Highdosesofcertaintoxicchemicals,suchasinsecticidesorbenzeneingasoline,
(sameeffect).
3.Autoimmunedisorders,suchaslupuserythematosus,
Theimmunesystembeginsattackinghealthycellssuchasbonemarrowstemcells,
whichmayleadtoaplasticanemia.
Inabouthalfofaplasticanemiacases,thecauseisunknown,aconditioncalled
idiopathicaplasticanaemia.

People with severe aplastic anemiausually have a poor prognosis:
They die unless they are treated with blood transfusion, which can
temporarily increase the numbers of RBCs or by bone marrow
transplantation.

c. Megaloblastic anemia/ pernicious anemia( Deficiency vitamin B12/folic acid
d.Hemolyticanemia
Different abnormalities of the RBCs,
Many of which are hereditarily acquired. They make the cells fragile, so they
rupture easily as they go through the capillaries, especially through the spleen.
The number of RBCs formed may be normal, or even much greater than normal
in some haemolytic diseases but the life span of the fragile RBC is so short that
the cells are destroyed faster than they can be formed, and serious anaemia
results.

•In hereditary spherocytosis
The RBCs are very small and spherical rather than being biconcave disks.
This type of RBCs cannot withstand compression forces because they do
not have the normal loose, baglikecell membrane structure of the
biconcave disks.
As they pass through the splenic pulp and some other tight vascular beds,
they are easily ruptured by even slight compression.

•Sickle cell anemia
•Ispresent in 0.3 to 1.0 percent of West African and American blacks,
the cells have an abnormal type of hemoglobincalled hemoglobinS,
containing faulty beta chains in the hemoglobinmolecule.
•When this hemoglobinis exposed to low concentrations of
oxygen, it precipitates into long crystals inside the RBC.
•The crystals elongate the cell and give it the appearance of a
sickle rather than a biconcave disk
•The precipitated hemoglobinalso damages the cell membrane,
so the cells become highly fragile, leading to serious anemia.

•Sickle cell disease crisis
•Such patients frequently experience a vicious circle of events
called a sickle cell disease “crisis,”:
•low oxygen tension in the tissues causes sickling, which leads
to ruptured RBCs, which causes a further decrease in oxygen
tension and still more sickling and RBC destruction.
•Once the process starts, it progresses rapidly, eventuating in a
serious decrease in RBCs within a few hours and, in some
cases, death.

•In erythroblastosis fetalis
•Rh-positive RBCs in the fetusare attacked by antibodies from an Rh-
negative mother.
•The antibodies make the Rh-positive cells fragile, leading to rapid
rupture and causing the child to be born with a serious case of anemia

•ABNORMAL FORMS OF HAEMOGLOBIN
Normal hemoglobins
Hemoglobinopathies
•Introduction
•A range of abnormal forms of hemoglobin exist, and these are conveniently classified
according to which component is defective.
Abnormal globin chains
•Hemoglobin is produced by genes that control the expression of thehemoglobin protein.
•Genetic defects in haemoglobinare the most common of all genetic disorders
•Defects in these genes can produce abnormal hemoglobin and anemia, which are
conditions termed "hemoglobinopathies".

•Many genetic abnormalities of globin chain synthesis exist, which either result
in :the impaired production of globin chains (thalassaemias)
or abnormalities in the structure of the globin chain (hemoglobinopathies).

•Structural defects in the hemoglobin molecule.
•Alterations in the gene for one of the two hemoglobin subunit chains,alpha
(a) or beta (b),are called mutations.
•Often, mutations change a single amino acid building block in the subunit.
•Most commonly the change is innocuous, perturbing neither the structure
nor function of the hemoglobin molecule. (minor)
•Occasionally, alteration of a single amino acid dramatically disturbs the
behavior of the hemoglobin molecule and produces a disease state.
Sickle hemoglobin exemplifies this phenomenon(major)

•Diminished production of one of the two subunits of the
hemoglobin molecule.
•Mutations that produce this condition are termed "thalassemias."
Equal numbers of hemoglobin alpha and beta chains are necessary
for normal function.
•Hemoglobin chain imbalance damages and destroys red cells thereby
producing anemia

•Normal hemoglobins
•Normal Hbsare tetramers of 2 alpha and 2 beta globin polypeptide chains
•alpha chains(2) : 141 amino acids
the genes that express alpha globin are located
near the short arm of chromosome 6
On the chromosome 6 : there are 3 genes within the alpha genes cluster
Zeta
alpha1
alpha2

•Beta chains(2) : 146 amino acidd
the genes that express beta globin are located on
the
chromosome 11
•On the chromosome 11
Five genes are within the beta cluster:
epsilon
2 gamma genes
delta gene
beta gene

Normal/ types of hemoglogins
•After 8 weeks of fetal live , embryogenic hemoglobinsare
formed:
Gower 1
Gower 2
Portland
At 9 weeks of fetal HbF is formed( major Hb)
At one month of fetal life : HbA appears but non dominant until
after birth, when the fetal Hb( HbF) starts to decline

•At birth : HbA
Predominant HbA1 (>95%)
Minor HbA2 (<3.5%)
HbF : though it predominates during the most of gestational
, it declines at birth and count for just a small fraction f total Hbin
adult red cells( 0.3-1.2%) and are restricted to a small subunit of
circulating RBCs referred to as F cells.

•Hemoglobinopathies
•Hemoglobinopathies are disorders affecting the structure, the
function, or the production
•Classifications
•I .Structural hemoglobinopathies
•are hemoglobinopathies with altered amino acids sequences
that result in deranged ,of physical or chemical properties.

•A.Abnormalhemoglobin polymerization :
HbS,
B.Alteredoxygen affinity
High affinity: polycythemia
Low affinity ; Cyanosis
C. Hemoglobin that oxide readily
1. Unstable hemoglobine: hemolytic anemia
2. M hemoglobine

Thalassemia syndromes
Thalassemia syndromes arise from decreased rate or absence of globin
chain synthesis and can result in moderate to severe anemia.
In health, equal quantities of alpha and beta-globin chains are produced.
Abnormalities in the transcription of either alpha or beta-globin genes
lead to the excessive production of the other chain, and these chains may
precipitate, causing haemolysisand anaemia.

•Beta thalassemia
•Beta thalassemia are autosomal inherited disorders of beta globinssynthesis
•Beta-thalassaemiais usually due to a single-gene mutation and results in the
reduced production of beta-globin chains.
In most case, the globin structure is normal but the rate of production is
reduced because of :
•decrease in transcription of DNA
•or abnormal processing of pre-mRNA
•Or decreased translation of mRNA leading to decreased HbA products

•In individual with beta thalassemia, there is either a complete absence of
beta globin ( thalassemia major) or partial reduction in beta globin
production( thalassemia minor)
•Pathophysiology
In the bone marrow
•Thalassemia mutation disrupts maturation of erythrocytes resulting
in uneffectiveerythropoiesis
•the marrow is hyperactive but relatively few reticulocytes and
anemia

•Alpha thalassemia
•Alpha-thalassemia is one of the most common hemoglobin genetic
abnormalities and is caused by the reduced or absent production of the
alpha globin chains.
•The deletion of between one and all four genes, with an associated
variation in clinical severity.
•There are clinical syndromes in thalassemia
Silent Carrier State
Alpha thalassemia trait ( Minor)
Hemoglobin H disease
Bart’s Hydrops Fetalissyndrome

•Silent carrier
•There is : deletion of single alpha-gene
Genotype a../aa
Asymptomatic
No RBC abnormality
Can only be detected by DNA studies
Thalassemia trait( Minor)
Deletion of 2 alpha-genes
genotype : _ _/aa or _a/_a
Asymptomatic or minimal signs
Minimal RBCs abnormalities

•Hemoglobin H Disease
•Second most severe form of the the alpha thalassemia
•Deletion 3 alpha-genes
•Genotype : _ _/_ a
•There is75% reduction of alpha chain/25% of alpha chain is
synthetized
•Small amount of HbF, HbA1, HbA2
•Severe anemia
•Severe RBCs abnormalities
•Fetus can still survive

•Bart’s hydrops Fetalissyndrom
•The most severe form
•Incompatible with life
•No function of alpha chain
•Baby born: edeme, hepatomegaly, cardiomegaly

•Sickle cell/anemia and disease
•Sickle cell anemia
•Is an autosomal recessive disease that result from the
substitution of the valine for glutamic acid at position 6 of beta-
globin chain.
•Sickle cell disease is a multisystem disorder that is caused by a single
gene mutation.
•Characterized by the presence of abnormal erythrocytes
damaged by HbS, this variant of normal adult hemoglobin (HbA)
is inherited either from both parents (homozygosity for the HbS
gene) or from one parent, along with another hemoglobin variant,
such as hemoglobin C (HbC), or with β-thalassemia (compound
heterozygosity).

WHITE BLOOD CELLS
PROPERTIES OF DIFFERENT TYPES OF WBC
Structure
Functions
Regulation
MATURATION AND DESTRUCTION OF WBC: LYMPHOCYTES

WHITE BLOOD CELLS
PROPERTIES OF DIFFERENT TYPES OF WBC

•We are exposed continually to bacteria, viruses, fungi, and parasites, all of
which occur normally and to varying degrees in :
the skin,
the mouth,
the respiratory passageways
the intestinal tract,
the lining membranes of the eyes,
the urinary tract.
Many of these infectious agents are capable of causing serious abnormal
physiological function or even death if they invade the deeper tissues.

•We are also exposed intermittently to other highly infectious bacteria
and viruses besides those that are normally present, and these agents
can cause acute lethal diseases such as pneumonia, streptococcal
infection, and typhoid fever.

•Defence system
•Our bodies have a special system for combating the different infectious
and toxic agents.
•This system is made of blood leukocytes white blood cells [WBCs]) and
tissue cells derived from leukocytes.
•These cells work together in two ways to prevent disease: (1) by actually
destroying invading bacteria or viruses by phagocytosis and (2) by
forming antibodies and sensitized lymphocytes that may destroy or
inactivate the invader.

Structure
WBC have nucleus and other organelles but don’t have Hb.
WBC= Leucocytes
Primary function: help the body defend against invasion of pathogens
and remove toxins , wastes and abnormal/damaged
cells.
Two groups : based on their appearance after staining
Agranulocytesand Granulocytes

Agranulocytes: (few or no granules)
Granulocytes ( abundant stained granules)
Characteristics of WBC
Their movement:
are able to travel along miles of capillaries and can detect chemical signs or
damage surrounding tissues.
1 Capable of amoeboid movement:
capable of rearranging their shape to fit in any environment and encompass the
enemy.
2 Can migrate out of the bloodstream
When activated in the bloodstream, they contact and adhere the vessel wall
(margination)

3. After entering the vessel wall, can squeeze between adjacent
endothelial cells (emigration, diapedesis)
4.chemotaxis
Chemotaxis is the movement of cells or organisms in response to
chemicals. It is the movement of leucocytes and macrophages toward
higher concentration of certain fragments of complement,
Guided by chemotaxis, leucocytes attack invading pathogens and damaged
tissues.

5.Phagocytosis: involved in phagocytosis are neutrophils, eosinophils
monocytes
Neutand Eosin = microphage as opposed to macrophages( large monocytes that
have moved out of the bloodstream)

•Phagocytosis: Cells engulf pathogens, cells debris and other materials

•TYPES OF WBC
•Some contribute to the body non specific defense
Neutrophiles
Eosinophiles
Basophiles
•Some are involved in specific defense of the body:
Lymphocytes

•NEUTROPHILS:( 50-55%)
Neutro: chemically neutral hence difficult to stain (acid/base)
Mature : have a dense , segmented nucleus with 2-5 lobes(polymorph
nuclear leucocytes)
Cytoplasm :
Their cytoplasm has pale granules containing lysosomal enzymes and
bactericidal components.
They are highly mobile cells and are the first to reach the site of an
injury.
They are very active cells , which can attack and digest bacteria that
have been marked by antibodies or complement(Plasma protein
involved in tissue defense)

•Process:
1.Encountering bacterium
They engulf, their metabolite rate increases
“Respiratory Burst”:
Respiratory burst is the rapid release of reactive oxygen species(ROS)
from different types of cells. Usually it denotes the release of these
chemicals from immune cells, e.g., neutrophils and monocytes, as they
come into contact with different bacteria or fungi.
Increase of o
2consumption through the activity of NADH-oxidase that
generates oxygen species : superoxide anion(O
-
2) and the oxygen
peroxide ( H
2O
2), which can kill bacteria

2. Meanwhile
•Vesicles containing engulfed pathogens fuse with lysosomes(digestive
enzymes and small amount of peptide: defensins)
•Defensins kill bacteria, fungi, bacteria and some viruses
•Digestive enzymes break down the bacteria remaint

1.Prostanglandines:increasecapillarypermeability,contributetolocal
inflammationandrestrictthespreadoftheinflammation
•2.Leukotriene:hormoneoftheimmuneresponsesystemthatattracts
otherpathogensandcoordinatestheimmuneresponse.
•Neutrophilsreleasealsotwoothersubstances:
•EOSINOPHILS(2-5%)
Theirgranulesstaindarklywitheosin(reddye):Theystainwithacid
dye(acidophile)
Activity:theyattackbacteriacoatedwithantibodies.
Phagocyticcells
Engulfantibodiesmarkedbacteria,protozoa,orcellulardebris

•But their primary mode of attack is the exocytosis of toxic compounds (
nitric oxide, cytotoxic enzymes)which adhere to the surface of their
targets.
•The number of eosinophils increases during infection and during allergic
reactions
•They control the spread of infection to adjacent tissues :
When attracted to the site of injury, they release enzymes to reduce the
degree of the inflammation
•BASOPHILS(1%) (BHH)
•Stain blackly with a basic dye.
•They migrate to the site of injury, cross the capillary membrane and
damage the tissue by discharging their granules in the interstitial fluid

•The granules contain Histamine : vasodilator
Heparin : anticoagulant
•Basophils release also other chemicals which attract eosinophils and
other basophils.
MONOCYES(1-8%)
•Have large nucleus
•Shape : oval/kidney bean
•The bloodstream is their highway where they remain for 24 hours then
get into peripheral tissue= Macrophages
•Macrophages are large monocytes . They are very active phagocytic
cells which can attempt to engulf larger items than themselves

•While activated they release chemicals that attract and stimulate
neutrophils, monocytes and other phagocytic cells.
•Activated macrophages secrete substance that lure fibroblasts(
involved in the healing process by forming scare)
•LYMPHOCYTES(20-30%)
•Larger than RBCs
•Lack granules
•Continuously migrate ( travel)from the bloodstream to the peripheral
tissues and back(patrolling)
•Sites : connective tissues and organs of the lymphoid system
Circulating lymphocytes(1% of all lymphocytes)

•Three classes of lymphocytes
T Cells.
T refers to (Thymus)
1.Responsible of cell-mediated immunity , a defense mechanism against
foreign body and tissues
2. Coordinate immune response
Mode: enter the periphery and attack directly tissues or
control the activities of other lymphocytes
B Cells( B refers to bone marrow/or bursa-derived)
B Cells( humoral immunity/antibodies)
Defense mechanism involving the production & distribution of antibodies
which attack the foreign antigens.

T-cells and B-cells
They recognize foreign specific antigen during antigen presentation.
In response to the identified invade , T-cells and B-cells generate specific
responses tailored to eliminate the (pathogen or pathogen infected cells)
Antigen processing and presentationis the process by which protein
antigenis ingested by anantigen-presentingcell (APC), partially digested
into peptide fragments and then displayed on the surface of the APC
associated with anantigen-presentingmolecule such as MHC class I or
MHC class II.

•Purpose
•Antigen presentationdescribes a vital immune process which is
essential for T cell immune response triggering. ...
•If there has been an infection with viruses or bacteria, the cell will
present an endogenous or exogenous peptide fragment derived from
theantigenbound to MHC molecules.

•The major histocompatibility complex (MHC) is a set of genes that
code for cell surface proteins essential for the acquired immune
system to recognize foreign molecules in vertebrates, which in turn
determines histocompatibility.

•Antigen-presenting cells(APCs) are a heterogeneous group of
immunecellsthat mediate thecellularimmune response by processing
andpresenting antigensfor recognition by certain lymphocytes such as
Tcells.
•ClassicalAPCs include dendriticcells, macrophages, Langerhanscellsand
Bcells.

T-helper cells and CytotoxcT cells
In response to the presence of the pathogen :
T-helpers will produce cytokines that direct the immune response
Cytotoxic T cells : produce granules containing enzymes which induce
death and of pathogen infected cells.

B Cells differentiate in Plasma Cells: produce antibodies
Antibodies can destroy antigens from any location.
Whereas T Cells have to migrate to their targets.
•Natural Killers (KN Cells) :
•Major role: defend the host from tumor and virally infected .
•They have the ability of distinguishing the uninfected cell by
recognizing major histocompatibility complex(MHC)
•Immune surveillance: detection and subsequent destruction of abnormal
tissues.
•Important in preventing cancer

Activation of NK cells:
•Interferons( type of cytokines)
When activated, the release cytotoxic granules
•They don’t require prior activation to kill cells which are missing MHC
class I( natural killer)

•PRODUCTION OF WBCs
•Origin of the Stem Cells : Bone marrow( hemocytoblast)
•Hemocytoblast(division): Myeloid Stem Cell…Progenitor Cell
Lymphoid Stem cell
Progenitor Cells

•Regulation of WBC production
•Factors regulating the production are not yet clearly understood
•Production of Lymphocytes T and B , in adult is regulated by the
exposure to antigens
•hormones : Colony-stimulating Factor (CSFs)
1. M-CSF : stimulate the production of monocytes
2. G-CSF : stimulate the production of granulocytes
3. GM-CSF : stimulate production of both granulocytes and
monocytes
4. Multi-CSF : Accelerates the production of granulocytes ,
monocytes, platelets and RBCs

•White blood cell count Low
•Normal white blood cells count helps the body to fight against several
infections and diseases.
•Normally there should be 4.500 to 10.000 white blood cells in 1 micro
liter of blood.
•Leukopenia: inadequate number of leucocytes (Low)
•But if the count of white blood cells decreases below this level it can
lead to leucopenia.( 4.500)
•Due to scarce WBC’s, the body is unable to fight against invading
pathogens, microbes or viruses.

•There are number of causes that lead to low white blood cell count.
Some of these causes are described below:-
•Chemotherapy not only kills cancerous cells but also healthy immune
cells reducing the WBC count.
•Aplastic anemia is one of the major causes that can reduce white blood
cells to a large extent.

•Damage to the bone marrow due to certain complications can reduce the
number of white blood cells.
•Autoimmune diseases such as Lupus react against healthy white blood
cells and produce antibodies to attack it.
•Epstein-Barr virus, tuberculosis and HIV are some of the types of viral
infections that can reduce the WBC count.

•White blood cell count High
•Leukocytosis: Excessive number of leucocytes(100000/microl)
indicate some forms of leukemia
If the count is higher than 100,000 leukocytes in a micro liter of blood,
it is considered as high white blood cell count: leukocytosis.
White blood cell count is elevated due to certain pathogens, microbes
or infections.

•Increasedwhitebloodcellcountcanbeanindicationofcertainforms
ofcancer(leukemia)
•Postmenopausalwomenwithelevatedwhitebloodcellcountsmay
beatanincreasedriskofdevelopingcertaintypesofcancer,including
breast,colorectal,endometrial,andlungcancers.

•High white blood cell count causes
•Acute lymphocytic leukemia is a kind of cancer which elevates WBC count
as it mainly affects the bone marrow.
Other cause include;
Tuberculosis, acute or chronic lymphocytic leukemia, myelofibrosis and other
bacterial infection
The use of certain drugs such as epinephrine and corticosteroids can
increase white blood cell count.
•Smoking and stress also increase white blood cell count.

•Summary
•Types of white cell blood (leucocytes)
Agranulocytes: Lymphocytes and monocytes
Granulocytes : Neutrophils, Eosinophils and Basophils
•Production : Stem cell
•Types of lymphocytes :
T Cells :cellular mediated immunity
B Cells : humoral immunity( antibodies)
Natural killers

Capacities(abilities)
mode of actions:
Amoeboid movement
Marginalization
Emigration/diapedesis
Chemotaxis
Respiratory burst
Antigen presentation

•Phagocytosis
•Release of bactericidal substances/ enzymes
•Solitary /coordinated action
•Regulation of WBC
Causes of increase of WBC count
Causes of decrease of WBC count

•LECTURE 5
PLATELETS AND FUNCTION
HEMOSTASIS ( MECHANISMS)
CLOTTING MECHANISM(INTRINSIC & EXTRINSIC PATHWAYS

•PLATELETS AND FUNCTIONS
•Structure: flattened discs, round(view from above), enucleate cells
spindle shape( cross section)
Also called thrombocytes
Role: clotting system
•Life span :9-12 days
•Each microliter : 150000-500000
•Average concentration :350000/microliter
less 80000: Thrombocytopenia
Above 1.000.000 :
Thrombocytosis( 1000000):
cancer , excessive production during infection, inflammation)

Functions:
•Transport of chemicals important to the clotting process
•Formation of temporary patch in the damaged vessels wall(platelet plug)
•Active contraction after clot formation
•Platelet production(thrombocytopioesis)
•Site : bone marrow
•Stem cell : Megakariocytes( large cell with enormous nucleus)
Maturation and growth …manufacture proteins, enzymes and
membranes

•Then begin shedding cytoplasm in small membrane-enclosed packets
•Gradually megakariocytesloose their cytoplasm, producing 4000 platelets
Regulation
•Factors influencing the the production of platelets formation
•Thrombopoietin or thrombocyte-stimulating factor( peptide produced in
the kidney), which accelerates the formation of platelets and stimulates
the production of megakaryocytes.
•Interleukine-6
•Multi-CSF

HEMOSTASIS
•Definition
•Phases : Vascular phase
Platelet phase
Coagulation phase

•HEMOSTASIS
•Is the process of cessation of bleeding by forming clots to prevent blood
loss throughout the wall of damaged vessels
•When a small blood vessel is injured a series of events takes place to lead
to the formation of a clot.
•Hemostasis consists of three phases.
1. Vascular phase
When a vessel is cut(transected) it triggers a response: the contraction in
the smooth muscle (vessels)
The local vasoconstriction : vascular spasm

•Vascular spasm(30 minutes)
Vessel diameter decreases
Blood flow can slow even stop
When endothelial cells contract they expose basalamina to the bloodstream
oCells release :chemical factors and hormones
Chemicals : ADP, Tissue Factor and Prostacycline
Endothelin: promote vascular spasm, muscle contraction
stimulate the division of endothelial cells, smooth
muscle cells and fibroblasts
. Endothelial cells become sticky

2.The platelet phase
•Platelets begin to attach to the sticky endothelial surfaces ( to the basal lamina)
and expose collagen
•Attachment of platelets ( Platelet adhesion)
•More platelets arrive and stick one to another( Platelet aggregation)and form a
platelet plug
•At the site platelets are activated and release various compound:
•ADP: stimulate platelets aggregation and secretion.
•ThromboxanA
2 and serotonine: Stimulate vascular spasm
•Clotting factors : Proteins with role in blood clotting
•Platelet-derived growth factor( PDGF): Promotes vessel repair
•Calcium ions : involved in platelets aggregation and in several steps of clotting
process

•Platelets phase is rapid: positive feedback(ADP, thromboxane, Calcium
stimulate more aggregation)
•Factors that control the growth of the platelet plug.
oProstacyclin: Prostaglandin, released by endothelial cell, inhibit
platelets aggregation
oInhibitory compound released by WBC
oCirculating enzymes that break down ADP near the plug.
oCompound when in large amount will inhibit plug formation( Serotonin in
high concentration will block the action of the ADP)

3. Coagulation phase
•It involves the clotting factors
Phase of blood clotting: complex sequence of steps

•For blood clotting to happen clotting factors are necessary.
•Clotting factors or procoagulants include Ca
2+
11 proteins , many of them
are proenzymes.
•Identification : by Roman numerals
•Ca
2+
: Clotting factor VI
Clotting Factors(3) : III,IV and VIII: synthetized in the liver
Clotting factors(2) :III and VIII : always present in the bloodstream
Activated platelets release 5 clotting factors: III,IV,VIII and XIII
( Platelets Phase)
Chain reaction(cascade) : Activation of a proenzyme, cretatesan enzyme,
which activates a second proenzyme ….
•

•PATHWAYS
•The cascades involve 3 pathways
Extrinsic pathway
Intrinsic pathway
Common pathway

Understanding the clotting system:
To know :there are 3 pathways Extrinsic , Intrinsic and Common
There is a start for and the end for each way
Common pathway is stimulated by either
extrinsic/intrinsic
In both pathways are involve calcium and other proenzymes once one is stimulated,
become an active enzyme or a complex which stimulate/activate other proteins(
cascade)
The end result of coagulation is the formation of stable fibrin which the after a
successful process of coagulation has to be dissolved

•Extrinsic pathway
caused by an external injury that causes blood to escape from the
vascular system
Intrinsic pathway
coagulation is initiated at the site of the injury in response to the
release of tissue factor

Pathway Start: substances involved and mechanism
Extrinsic pathway Release of TF (Tissuefactor) by damaged endothelial cells
or peripheral tissue
Then : TF +Ca
2+
+ Factor VII =Tissue Factor Complex
Tissue factor complex activates Factor X
( common pathway)
Lab: Test :aPartialThromplastinTime (a PTT)
Intrinsic pathway Site of injury :
Activation of proenzymes (Factor XII) exposedto collagen
Process assisted by : PF-3: released by aggregated PLTs
Then series of reaction / activation :
presence of ca
2+
, Factor VIII & IX ( activated) leads to the
formation of Factor X activator complex,…( common
pathway)
Lab Test : Prothrombin Time (PT)

Pathway Start/ Substances involved / mechanism
Commonpathway Starts:
Enzymes for Intrinsic/ Extrinsicactivate Factor X
= Enzyme complex : Prothrombinase…
Converts Proenzyme Prothrombin into Thrombin
Thrombin stimulate/activate FibrinogenintoFibrin
To stabilize Fibrin: Fibrin Stabilizinng Protein

•Clot retraction
Once fibrin has been formed , platelets and blood red cells stick to the fibrin
strands
Platelets then contract and the entire clot begin to undergo clot retraction
(20-60 minutes)
Steps of clot retraction
1.Pulling of the torn edges of the vessels closer together, reducing
residual bleeding and stabilizing the injury site
2. Reducing the size of the damaged area , to allow fibroblasts, smooth
muscle cells, and endothelial cells to complete repair.

Feedback control of the blood clotting
Common pathway: Thrombin
Thrombin will stimulate blood clotting by:
Stimulating :the formation of tissue factor and
the release of PF-3(by platelets)
•The stimulation of the common pathway will stimulate intrinsic and extrinsic
pathway( Positive feedback to accelerate clotting factor formation and
reducing blood loss during severe injury)
•Blood clotting restriction
By factors : deactivate or remove the clotting factors
By other stimulatory agents

•Stimulatory agents :
Anticoagulants , plasma enzymes that inhibit clotting
Antithrombin-III inhibits several factors( thrombin…)
Heparin( Basophils and mast cells): cofactor , accelerate
the activation of antithrobin-III
Clinically : Used to impede or prevent clotting
Thrombomodulin( endothelial cells) + Thrombin,
thrombin , converted to an enzyme that accelerates
Protein C( plasma protein) , inactivates several clotting
factors and stimulates the formation of plasmin(enzyme)
that gradually breaks down fibrin strand

•Stimulatory agents
Prostacyclin(platelets phase) :inihibitsplatelets aggregation
opposes stimulatory action of thrombin,
ADP, other factors
•Proteins with anticoagulants properties
alpha-2-macroglobulin(inhibits thrombin)
C
1inactivator( inhibits several factors of the intrinsic pathway

•ABNORMAL HEMOSTASIS
I .Excessive or abnormal blood clotting
In case blood clotting is inadequately controlled or, blood clots will start
forming in the bloodstream
The blood clots will not stick to blood vessels walls but , move around ,
if not digested by plasmin, they become stuck in small vessels and form
an abnormal mass within the bloodstream( embolus) .
When the embolus blocks the circulation to the area downstream( the
blockage is called embolism

•Infarct: Tissue damage as a result of interruption of circulation
Infarct at the brain: Stroke
infarct at the heart : Myocardial infarction or heart attack.
•Embolus in the vein system, may lodge in one of the capillaries of the
lung : Pulmonary embolism
Thrombus(clot)
The platelets can begin to stick to the wall on an intact blood vessel
They are attracted on to the plaques( where endothelial and smooth
contain large quantities of lipids)
The thrombus can grow big and project in the lumen of the blood vessel
(circulatory blockage)

Treatment of circulatory blockage
1.Heparin
2.Coumadin ( warfarin) and dicoumarol: depress the synthesis of
several clotting factors by blocking the action of vitamin K.
3.Recombinant DNA-synthetized tissue plasminogen activator(t-PA)
4. Streptokinase and urokinase(enzymes), convert plaminogento plasmin

5. Aspirin : inactivates platelets enzymes involved with
the production of thromboxane and prostaglandins
inhibits the production of prostacyclin
5. Clotting can also be controlled within a blood sample:
Blood sample can be stabilized temporarily by adding heparin or
EDTA (Ethylenediaminetetroaceticacid)
EDTA removes ca
2+
from plasma, prevent clotting
CPD ( Citrate phosphate dextrose is added to a unit of whole blood
meant to be held for an extended period of time.( ties up plasma Ca
2
)

II. Inadequate blood clotting
a.HEMOPHILIA
•Hemophilia is an inherited disorder characterized by inadequate production
of clotting factors.
It affects 1/1000 and in 80-90% the factor VIII is inadequately produced
Severe cases : extensive bleeding after slight trauma or bleeding occurs
spontaneously
Sites : joints, around the muscles
Treatment : Transfusions
Clotting factor
Plasma samples
( however risk of blood borne diseases: AIDS, other viral infection)

•b. Von Willebrand disease(vWD)
•Von Willbrand disease(vWD) is the commonest inherited coagulation
disorder
•It is caused by the deficiency or dysfunction of the protein termed
von Willebrand factor
•VnWillebrand factor is a large glycoprotein, that circulates in the
blood plasma( approximate concentration :10 mg/ml).
It is stored in granules in platelets and endothelial cells

•It plays two major roles in hemostasis
1.Mediates the adhesion of platelets to the site of vascular injury
2.It binds and stabilizes the procoagulant protein factor VIII
Clinical manifestations
Nose bleeding
hematomas
Prolonged bleeding from trivial wound, oral cavity, excessive menstrual
bleeding
Rare : GIT bleeding

•Treatment
•Administration of pooled Factor VIII( contains normal vWF)
•In some forms, vWFis produced but plasma level ,are very low:
nasal spray ( containing synthetic form of ADH)
ADH appears to release vWFfrom the endothelial cell
Other treatment : DDAVP(Desmopressin)
Recombinant von Willebrand factor(rVWF)
von Willebrand Factor/ Factor WIII

•Calcium ions, Vitamin K andand blood clotting
•Calcium and vitamin K are involved with almost every aspects of the clotting
process
•The 3 pathways require calcium.
Vitamin K: must be present in the liver for the synthesis of clotting factor
, prothrombin
Any deficit of vitamin K will cause the breakdown of the common pathway ,
ultimately deactivates the entire clotting system

•Fibrinolysis( process of dissolving the fibrin)
Repairs continue and the clot gradually dissolves.
Fibrinolysis begins with the activation of the plasminogen( proenzyme)
Two enzymes :Thrombin( produced by the common pathway)
Tissue plasminogen activator (t-PA), releases by damaged
tissues at the site of the injury
Plasminogen activation …plasmin(enzym)…begin digesting the fibrin
strand and eroding the foundation of the clot.

LECTURE 6: I.BLOOD GROUPS: AOB GROUPING
IIRHESUS BLOOD GROUPING AND ERYTHROBLASTOSIS
FOETALIS
III.BUFFERING PROPERTIES OF THE BLOOD

•OUTLINE
•Definitions : Antigen
Antibody
Immune system
•Blood types
Determination of blood types
Blood compatibility
Cross-match reaction

•BLOOD GROUPING/TYPES
•Definitions
•Antigen:a substance that can trigger immune response, defense
mechanism that protects from attack( infection…).
•Most antigens are proteins, glycoprotein, carbohydrates, glycolipids.
•Human cells membrane including Red Cells contain surface antigen
•The immune system can recognize as normal and does not attacK
them

•The immune system
The immune system is the host system which comprises biological structures
and processes within the organism that protect against diseases, bacteria,
virus, foreign substances…
Antibody
The antibody is a protein produced mainly by plasma cells used by the
immune system to identify and neutralize(stop harm or kill) pathogens.
Agglutinin
An agglutininis a substance that causes particles to coagulate to form a
thickened mass.
Agglutinin : can be antibodies that cause antigens to aggregate by binding to
the antigen-binding sites of antibodies.
Or any substance other than antibodies such as sugar-binding protein lectins

•Antigenicity Causes Immune Reactions of Blood
•Blood transfusions from one person to another were first attempted.
Immediate or delayed agglutination and hemolysisof the red blood
cells often occurred, with typical transfusion reactions that frequently
led to death.
•What was discovered is:
•the bloods of different people have different antigenic and immune
properties, so that antibodies in the plasma of one type blood will
react with antigens on the surfaces of the red cells of another blood
type.

•By taking proper precautions , one can determine ahead of time
whether the antibodies and antigens present in the donor and
recipient bloods will cause a transfusion reaction.

•BLOOD TYPES AND ANTIGEN/ANTIBODY
•Ithavebeenfoundinhumanbloodcells,especiallyonthesurfacesof
thecellmembranesatleast30commonlyoccurringantigensand
hundredsofotherrareantigens.
•Eachofwhichcanattimescauseantigen-antibodyreactions.
•Mostoftheantigensareweakandthereforeareofimportance
principallyforstudyingtheinheritanceofgenestoestablish
parentage.

•A and B Antigens /Agglutinogens
•Two antigens(type A and type B) occur on the surfaces of the red
blood cells in a large proportion of human beings.
•These two antigens (also called agglutinogens because they often
cause blood cell agglutination) cause most blood transfusion
reactions.
•Because of the way these agglutinogens are inherited, people may
have neither of them on their cells, they may have one, or they may
have both simultaneously.

•Blood groups/Types
There is a total of 35 human blood groups systems. The two important
are the ABO and the Rh antigen ( Rhesus factor).
A blood group/type is a classification of blood based on the presence or the
absence of antibody or the presence or the absence of inherited antigenic
substance(antigen)
Inherited(contribution from both parents)
The antigen can be at the surface of an other cells:
Salivary glands, pancreas, liver, lung,semen…
The antibodies involved are IgM

The ABO system determines blood type :
A,B,AB,O + Rhesus factor
with(+/-)denoting the presence or the absence Rhesus factor
The complete type is recorded e.g: ORh+ or O
+

•ABO system
•Karl Landsteiner (1900) is the first to discover and to describe the
ABO blood group system
•Alfred von Decastello and Adriano Sturli, discovered later the AB
group.
•The ABO blood types classification is the most adopted but some
countries , use the roman numbers I, II, III, IV to name the blood
groups…

Determination of blood type/group
The blood groups are inherited from both parents.
Genetics:
The ABO system is controlled by ABO gene
The ABO gene controls/encodes a specific enzyme :
Histo-blood group system transferase which has glycosyltransferase activity
Activity : the determination of blood type happens by modifying the
oligosaccharides on the cell surface glycoproteins

Thevariationofsequenceofproteinsbetweenindividualsdeterminesthe
bloodtype/thegroup.
ABOgenehas3variantsforms(alleles)
AlleleI
A
givestypeA
AlleleI
B
givestypeB
AlleleigivestypeO
I
A
andI
B
aredominantoveriandasresultonlyindividualwithiigenotypehave
typeO

•Subgroup
•Phenotype A Phenotype B
•I
A
I
A
and iI
A
I
B
I
B
and iI
B

•Origin of Agglutinins in the Plasma.
•The agglutinins are gamma globulins, and they are produced by the
same bone marrow and lymph gland cells that produce antibodies to
any other antigens.
•Most of them are IgM and IgG immunoglobulin molecules.
•Small amounts of type A and B antigens enter the body in food, in
bacteria, and in other ways, and these substances initiate the
development of the anti-A and anti-B agglutinins.

Relative Frequencies of the Different Blood Types.
•The prevalence of the different blood types among one group of
persons studied was approximately:
O 47%
A 41%
B 9%
AB 3%
The O and A genes occur frequently, whereas the B gene is infrequent.

Phenotype Genotype
A AA or AO
B BB or BO
AB AB
O OO

Group blood compatibility
In clinical practice it is important to determine/know the correct blood
group prior to transfusion as failure to do so will result in serious / fatal
adverse reactions
Blood grouping and blood matching
Before transfusion, it is necessary to determine the blood type of the
recipient’s blood and the blood type of the donor blood so that the
bloods can be appropriately matched.
This process id called blood typing and blood matching, and these are
per-formed in the following way:

•Blood grouping and blood matching
1.The red blood cells are first separated from the plasma and diluted
with saline.
2. One portion is then mixed with anti-A agglutinin and another portion
with anti-B agglutinin.
After several minutes, the mixtures are observed under a micro-
scope.
Result: If the red blood cells have become clumped—that is,
“agglutinated”—one knows that an antibody-antigen reaction has
resulted.

Cross-Reaction
By receiving foreign RBCs , the antibodies (agglutinin)will attack the
foreign antigens ( Agglutination)
When antibody meets its specific antigen, the RBC agglutinates and
even hemolyse
e.g: anti-A antigen + A surface antigen (RBC)
The RBC carrying the antigen clump even burst
To avoid /prevent the incident to happen, tests should be performed to
ensure that donor’s and recipient's are compatible

•Agglutination(Greck: gluing to …)
•Is the process that takes place in the presence of an antigen with its
coressponding antibody
•In the presence of an antibody or complement the bacteria or the
erythrocytes clump even burst( hemolysis)
RBCs
When wrong blood group is trnasfused to a person,the antibodies react
with the incorrect group blood , the erythrocytes clump and stick
together causing the to aggluninate

•Testing for compatibility
•The cross-reaction can be life threatening. To prevent this this to
happen compatibity test should be performed in advance
•Procedure
a. Determine the blood group
b. Cross match test
1 drop of blood mixed separately with
solutions containing anti-A antibodies
anti-B antibodies
anti-Rh
•Any cross reaction is recorded

•The Rhesus System ( Rh system)
•The Rh blood group system is one of the most polymorphic and
antigenic blood group systems.
•The rhesus system is the second most significant blood-group
system in human system and probably the most complex of all
erythrocyte blood groups , with currently 50 antigens.
•It is well known as a primary cause of hemolytic disease of the fetus and
newborn (HDFN).
•D antigen, is the most significant antigen and the most likely to
provoke an immune response

•The terms Rh positive and Rh negative refer to the presence or absence of D
antigen.
•Role/function: to maintain structure integrity of the RBCs
may play a role in ammonium and carbon dioxide transport

•The major difference between the O-A-B system and the Rh system is
the following:
•In the O-A-B system, the plasma agglutinins responsible for causing
transfusion reactions develop spontaneously, whereas in the Rh
system, spontaneous agglutinins almost never occur.
•The person must first be massively exposed to an Rh antigen, such as
by transfusion of blood containing the Rh antigen, before enough
agglutinins to cause a significant transfusion reaction will develop.

•RhImmuneResponse
FormationofAnti-RhAgglutinins.
WhenredbloodcellscontainingRhfactorareinjectedintoaperson
whoseblooddoesnotcontaintheRhfactor(intoanRh-negative
person)anti-Rhagglutininsdevelopslowly,reachingmaximum
concentrationofagglutininsabout2to4monthslater.
Thisimmuneresponseoccurstoamuchgreaterextentinsomepeople
thaninothers.
WithmultipleexposurestotheRhfactor,anRh-negativeperson
eventuallybecomesstrongly“sensitized”toRhfactor.

•Clinical Significance
•The D antigen is, after A and B, the most important red cell antigen in
transfusion practice.
•Individuals who lack the D antigen do not have anti-D in their serum.
•The antibody is produced through exposure to the D antigen usually
as a result of transfusion or pregnancy.
•The immunogenicity (ability of antigen to stimulate production of
antibody) of D is greater than that of virtually all other red

•Four additional genes are recognized as belonging to the Rh system
and they are: C, c, E and e. Named to follow precedent of giving
letters of alphabet to blood groups.
•These antigens and their corresponding antibodies characterize the
Rh blood group system and account for the majority of Rh antibodies
encountered in blood banking.

•Other Rh antigens
•Patientsarenotroutinelytypedfortheseunlesstheyhavedeveloped
atypicalantibodiesorarefacinglong-termtransfusionsupportfor
diseasessuchasmyelodysplasiaorsicklecelldisease(SCD).
•Inadditiontothefiveprincipalantigens(D,C,c,E,ande),morethan
50otherRhsystemantigensareknown.

•Rh blood group:
•Over 50 known antigens
•Highly polymorphic
•D, C, c, E, e most important
•RHD gene codes for presence or absence of D polypeptides
•RHCE gene codes for Ce, cE, ceor CE polypeptides
•RHAG gene produces an Rh-associated glycoprotein and serves as a
coexpressor

•Weak D ( quantitative difference in D antigen)
•Characterized by negative reaction with anti-D reagent spin
negative reaction after 37
0
c intubation
but positive reaction at anti-human globulin (AHG) phase.
Partial D(qualitative difference in D antigen)
Due to an alteration in D-epitopes
alteration of the protein structure
Rh null phenotype
This phenotype does not Rh antigen on their RBCs ,their proteins have some
abnormalities,
It can result in hemolytic anemia

Distribution among races
Caucasians of European :
have the highest incidence of the Rh-negative phenotype (15% to 17%),
Africa (5%)
Rh-negative type is much less common in Africa and Australia and is
considered a rare blood type not routinely tested for in some parts of Asia
( 1%).
In American blacks, the percentage of Rh-positives is about 95, whereas in
African blacks, it is virtually 100 per cent.

•History
•The first human example of the antibody directed at the D antigen
was reported in 1939 by Levine and Stetson, who found it in the
serum of a woman whose fetus had fatal hemolytic disease of the
newborn.
•The Rh system was identified by the work of Landsteiner and Wiener
who found that human RBCs were agglutinated by an antibody,
apparently common to all rhesus monkeys and 85% of humans.
•This factor was named the Rh factor.

•Landsteiner and Wiener immunized guinea pigs and rabbits with the
RBCs of Rhesus monkeys, the antibody produced by these animals
agglutinated 85% of human RBCs.
•Later the antigens detected by the rhesus antibody and by the human
antibody were established as dissimilar, but the system had already
been named.
•This contribution to medical science was the most significant event in
blood group systems research since the discovery of the ABO system
40 years earlier.

•Human anti-Rh and animal anti-Rh are not the same.
•However, “Rh” was embedded into blood group antigen terminology.
•The animal anti-Rh antibody was renamed “anti-LW” for Landsteiner
and Wiener.
•Rhesus macaque

Hemolytic Disease of the Newborn
•Erythroblastosis fetalis is a potentially life-threatening blood disorder
in a fetus or newborn infant.
Erythroblastosis fetalisdevelops in an unborn infant when the mother
and baby have different blood types.
•The mother produces antibodies that attack the developing baby's
red blood cells.

•Erythroblastosis fetalis is a disease of the fetusand newbornchild
characterized by agglutination and phagocytosis of the fetus’sred blood
cells.
•In most instances of erythroblastosis fetalis, the mother is Rh negative and
the father Rh positive.
•During pregnancy, if the mother is Rhesus-negative,herimmune system will
not tolerate the presence of fetalRh-positive red cells.Ittreat them asif
they were froreignsubstance and makes antibodies against them.
( and the mother develops anti-Rh agglutinins from exposure to the fetus’s
Rh antigen.)
•

•In turn, the mother’s agglutinins diffuse through the placenta into the
fetusand cause red blood cell agglutination.
•First born: are often not affected,becauseit takes time for the mother
to develop antibodies ..unless the mohermiscarriage
•Second fetus , mother Rh-negative, fetus or neonate(Rhesus positive)
may be affected.

•A Rh+ mother( no anti-Rh anti bodies) can carry a Rh-fetus without
difficulty)
•When mother Rh-carries a Rh+ fetus
•Sensitization occurs at delivery, where blood of the mother and the
fetus mix, the mother’s immune system can be stimulated to produce
antibodies .
Within six months after delivery, nearly 20% of Rh-,who carried Rh+ fetus
would have been sensitized
During pregnancy some RBCs in fetus cross into mother’s bloodstream
but the amount produced is not significant to stimulate the production of
antibodies.

•Second pregnancy
•Rh-mother , Rh+ fetus,
mother’s anti-Rh antibodies cross the placenta and enter fetus
bloodstream
Result: fetus RBCs destruction, anemia
Fetus demand for RBCs increases , RBCs begin leaving the bone
marrow before they mature(erythroblasts), hence the name HDN
is also called erythroblatosisfetalis

•Clinical manifestations at birth:
Anemia
Jaundice resulting from fetus RBCs destruction
Treatment:
Because mother’s antibodies may be active for one or two months:
Fetus blood should therefore: (transfusion)
If fetus is in danger of surviving after delivery, delivery can be induced at
7 or 8 months.
Anti-Rhesus antibodies can be given to mother in the last three months
of the pregnancy , during and after delivery..

LECTURE 7: IMMUNE FUNCTION AND NON SPECIFIC DEFENCES
INFLAMMATION
INFLAMMATORY RESPONSE
IMMUNE RESPONSE
LECTURE 8: CELL MEDIATED IMMUNE RESPONSE
ANTIBODIES AND MECHANISMS OF ACTION OF ANTIBODIES
IMMUNOLOGICAL MEMORY
ALLERGY AND AUTOIMMUNE DISORDERS
LYMPH FUNCTION

•LECTURE 7: INFLAMMATORY AND INFLAMMATORY RESPONSE
IMMUNE SYSTEM/ IMMUNE RESPONSE

Immunity and immune response
•Immune system ( definition)
Comprises two systems(mechanisms)
Innate immunity(nonspecific)
Adaptive /acquired immunity(specific)
Cellular immunity& humoral immunity

Several plasma protein and cellular systems contribute to non-adaptive immunity:
•Plasma protein systems:
complement system
coagulation system and fibrinolytic system
kinin system
•Cellular systems:
polymorphonuclear granulocytes (PMN):
(neutrophyls, eosinophils &basophyls)
mast cells
endothelial cells
platelets (thrombocytes)
macrophages
dendritic cells
NK (natural killer) cells and other innate
lymphoid cells

•Granulocytes :
•contain small particles that are released during infection,allergic
reactiinsand asthma

•Several of these cell types share molecular systems that are necessary
for their defensefunctions.
•Collectively, these are designated "mediators of inflammation".
•They are either preformed or newly synthesized on demand.
•These molecules in fact cause inflammation, but their ultimate goal is
of course not inflammation, but defense.
•Hence Inflammation is just a transitory state that makes it easier to
combat infectious agents.
•All these molecules greatly overlap in their functions.).

Cellular subsystems contributing to defense/ inflammation mediators:
•Preformed molecules are stored in granules and released when necessary:
vasoactive amines: histamine, serotonin
lysosomal proteins
•Newly synthesized molecules:
prostaglandins and leukotrienes
platelet activating factor (PAF) •
reactive oxygen species (ROS)
NO
Cytokines
Type I interferons

•Innate immunity(from birth)
This type of immunity is nonspecific, prevents/ attacks or
destroys any agent perceived as foreign or harmful. It is quick response
toward a pathogen.
Body first barriers: skin, epithelial
mucosal layers
stomach: secrets acid( low pH)to kills pathogens
natural flora(bacteria)
Immediate response(quick response)
if the first barrier is broken, pathogens enter
the body , other barriers(cells, biochemicals
take over)

•Response: the cells detect pathogens and kill them
Innate immunity(types)
Always on : physical barriers
Complement ( proteins to target bacteria)
Immediate response: develops rapidly when bacteria enter the
body. Cells are activated,
neutrophils(phagocytes,engulfand destroy the pathogen)
APCs(antigen presenting cells) bind the
harmful bacteria and present to other
phagocytes.

Categories of defenses:
1.Physical barriers
2.Phagocytes
3.Immunological surveillance(NK)
4.Interferons: chemical: messengers , coordinate the defense
against viral interference
5.Complement : system of circulating proteins that assist
antibodies in the destruction of pathogens.
6.Inflammation
7.Fever

•1. Physical barriers:
•Skin, epithelial tissues
Internal : GIT :tight junctions supported by fibrous basal lamina
Epithelial surface : secretions and pH, destructive enzymes
bactericidal materials
Mucosa(respiratory system) : continual clearance ,(flush out)
Hair

2.Phagocytes
Remove debris and pathogens
Microphages: neutrophils and eosinophils
Neutrophils first cells to arrive on the site , are more++
Eosinophils target compounds/pathogens coated with
antibodies
Macrophages: Monocytes…circulation
Almost every tissue in the body hosts residents/visiting macrophages
There is a relative diffuse collection of phagocytes that form a system:
Monocyte-Macrophage system or Reticuloendothelial system

•Response of macrophages:
a.Engulfpathogens /FB anddestroy them with lysosomal enzymes
b.Bindto remove pathogens/ destroy with the help of other cells
c.destroyforeign bodies/pathogens by releasing TNF,NO, H
2O
2in the
interstitial fluid
Types of macrophages
a. Fixed macrophages (histiocytes): permanent residents of tissues/organs
incapable of movement
Locations : connective tissues in close association with collagen and reticular fibers.
Special names : Microglia : Macrophages in the CNS
Kuppfer cells : Macrophages around liver sinusoids.

b. Free macrophages : mobile, travel throughout the body
Some tissues contain free macrophages with distinctive
characteristics. E.g:
The lungs surface have alveolar macrophages ( phagocytic dust cells).
During infection these Free macrophages can loose their
attachment and travel until they find damage tissues.
Movement of cells and phagocytosis
Diapedesis
Chemotaxis
Adhesion

3.Immunological surveillance(NK)
Immunological surveillance is the constant monitoring of normal tissue by NK.
Any abnormal tissue that appears in peripheral tissue will be recognized and
killed by (NK)
NK will respond to any antigen membrane on the abnormal tissue(No Specific)
As result NK attack bacteria, viruses, cells cancer…
They respond faster than lymphocytes T, B.

4.Interferons ( antiviral)
Interferons are small proteins released by lymphocytes, macrophages, cells
tissues infected with viruses.( in the presence of viruses)
Macrophages :produce alpha-interferon
Epithelial cells : produce beta-interferons
T-lymphocytes :produce gamma-interferons

Main function : to stop the spread of viral infection.
Interferons will bind the membrane of abnormal tissues and then activate the
production of antiviral proteins(cytoplasm)
•Interferons produced in response to one virus will protect against many other
types of viruses, and for this reason, interferon is considered a nonspecific
form of defense.
•The interferons do not directly inhibit viruses. Instead, they stimulate
adjacent cells to produce substances that inhibit the replication of viruses in
those cells.
e.g: Stimulate the activities of macrophages and of NK cells.

•5. Complement system
•Thecomplementsystemispartoftheinateimmunesystem(vsadapative)
•Itisnamed“complementsystem”becauseitwasfirstidentifiedasaheat-labilecomponentof
serumthat“complemented”antibodiesinthekillingofbacteriaI.
•Henceitprimarilyservestofightbacterialinfectionanditworksatseverallevels.
Itisnowknownthatitconsistsofover30proteinsandcontributes3g/Lto
overallserumproteinquantities.
Mostoftheseproteinscirculateinaninactiveform,butwhenactivatedtheyactinconcert
orderlysequencetoexerttheirbiologicaleffects.
Theactivationofoneprotein,enzymaticallycleavesandactivatethenextproteininacascade.

The complement system can be activated by at least three separate
pathways. The two evolutionary older pathways are the so-called:
"alternative" and the lectin pathways.
Both are activated on many bacterial surfaces, contributing to innate
immunity.
The third pathway, which is mainly antibody-activated and hence part
of the adaptive immune system, developed much later, but was
identified first.
Somewhat unfairly, it is therefore called the "classical pathway".

•More important : C
1 ….C
9
•Factor B, Factor D, Factor H, Factor I
•Properdin, C1 inhibitor, C9 binding protein, S protein

•The proteins that are produced have three functions:
1.They help kill invading organisms by opsonization, chemotaxis, and
eventual lysis of the cells;
2.They serve in part as a bridge from innate to acquired immunity by
activating B cells and aiding immune memory;
3. They help dispose of waste products after apoptosis ( death of cells
which occurs as a normal and controlled part of an organism’s growth
or development)

Classical pathway
The classical pathway is the most effective and rapid way
through which the complement system is activated
It begins with the interaction between the antibody and antigen
at cell surface and ends with the lysis of the cell.
Cell membrane : AB-Atg----lyse of the cells

•Classical pathway
1.Antigen-antibody complex binds to C1
2. C1 cleaves C4 : C4a (smaller fragment) and C4b (larger fragment)
3. C1 combines with C4b= C14b
C14b is an enzyme that converts C2 into C2a and C2b
4. C14b combines with C2a = C14b2a ( C3 convertase)
C3 convertase converts C3 in C3a( smaller fragment) and
C3b(large fragment)
C3 convertase formed by the pathway(C4b2a) splits C3 in 2
•fragments : C3b large : can attach covalently to the surface
of microbial surface and opsonize it

C14b2a combines with C3b = C5 convertase
5. C5 convertase converts C5 in C5a and C5b(large fragment)
6. C5b combines with C6, C7, C8, C9 = C5b6789 =
Membrane attack complex(MAC)

•The alternative pathway( Properdin pathway)
Less effective and slower activation of complement
Occurs in the absence of antibodies.
Defense against ; bacteria, viruses, parasites
Properdin ,factor P, factor B, factor D
End : Conversion C3 into C3b: stimulate phagocytosis
formation of membrane attack complex

•Alternative pathway is triggered by bacterial endotoxin which
lipopolysaccharide compound found in gram negative bacteria
•Step 1 : spontaneous hydrolysis of factor C3 (blood plasma) into C3b
•Step 2 : Factor C3b combines with Factor B
3. Factor B cleaves into Ba and Bb
Bb+ C3b = C3bBb = C3 convertase…converts C3 into C3a and C3b
4.C3b combines with C5 : C5 convertase : C5a + C5b
5. C5b+6+7+8+9 = C5b6789 = MAC

LECTIN MANNOSE PATHWAY
This pathway depends on the presence Mannose binding Lectin(MBL)
Microorganisms like Nisseria,Candida, salomonellahave carbohydrates(
Mannose, glucose..)
When they enter the human body, MBL recognizes them and MASP(
Mannose Associate Serum Protease) which then activate and cleaves
C4 and C2 in C4a,C4b and C2a,C2b
C4b combines with C2a = C4bC2a = C3 convertase
C3 convertase converts C3 into C3a and C3b

•C3b combine with C5 = C5 convertase : C5a+ C5b
•C5b+6+7+8+9 = C5b6789 = MAC

Effects of various end-products of the complement
1.Opsonization: C3b
Strongly activates phagocytosis by neutrophils and macrophages
2.Lytic complex( C5b6789= MAC)
•Rupture cell membranes of bacteria and other invading pathogens
3. Chemotaxis( fragment C5)
•This fragment will cause more neutrophils and macrophages to migrate at
the region of an antigen , attracting more other cells
4. Activation of mast cells and basophils ( C3a,C4,C5)
•When activated these cells , release histamine, heparin :Increased blood flow
Increased leakage plasma and proteins in interstitial tissues
The local tissue reaction helps inactivate and immobilize antigen agent.

5. Agglutination ( almost all end products)
change the surface of invading micro-organisms causing them to
adhere one to another.
6. Neutralization
Some end-products can attack the structure of some viruses and
render them nonvirulent
7.Activation of Mast cells and Basophils
C3a, C4a, C5a have direct effect on activation of mast cells and
basophils which then release a large amount of mediators of
inflammation( histamine, serotonine)… enhance the immune response

6.INFLAMMATION
Definition
Inflammation is the response triggered by damage to living
tissues. It is a complex localized response to foreign agents,

The purpose of the inflammatory response is to control and
eradicate the invading agent.
•After an injury /invasion by agents, the area is isolated while
damaged cells , tissues components and any dangerous
microorganisms are cleaned up.
•Inflammation can be produced by many stimuli :
abrasion, distortion, chemical irritation, infection by pathogen,
extreme temperatures

Inflammatory response involves cells , proteins and other
biochemical activities. It is a mechanism of defense that evolves
in phases and includes a sequence of reaction involving:
Cytokines, neutrophils
adhesion molecules
Complement and IgG
PAF

The invasion of the body by foreign agents(bacteria,virus, protozoa) triggers
the inflammatory response:
Bone marrow is stimulated:
production and release of cells: neutrophils
Chemotaxis: Bacteria products interact with plasma proteins and
cells to produce agents that attract more neutrophils
Chemokines( agents responsible for chemotaxis) are :
C
5a: component of complement system
leukotrienes
Polypeptides from cells(neutrophils, lymphocytes and basophils)

•Opsonisation: process by which some plasma factors act on
bacteria to make them tasty to phagocytes
Opsonins: agents that make bacteria tasty
Imunoglobulins: IgG
Complement proteins
Once the bacteria is coated(opsonin) to the neutrophil receptor
Response , mediated by G protein:
Increased motor activity of cells
Exocytosis

•Increased motor activity leads to prompt ingestion of the bacteria
by endocytosis , which is one of the modes of phagocytosis
•By exotocytosis
Neutrophils discharge their contents(granules) into the phagocytic
vacuoles(containing bacteria)= degranulation
Granules contain: various proteases
antimicrobial proteins( Defensins: alpha&beta)

•RESPIRATORY BURST
•The cell membrane-bound enzyme nicotinamide adenine dinucleotide
phosphate (NADPH) oxidase is activated, with the production of toxic
oxygen metabolites.
•The combination of the toxic oxygen metabolites and the proteolytic
enzymes from the granules makes the neutrophil a very effective killing
machine.

Inflammatory response.
Steps
1.Mast cells : stimulated by chemical and chemical changes
Response : Release of histamine, heparin, prostaglandins
histamine(vasodilator) increases capillary permeability
and accelerates
Increases flow: more cells on the site and the
carrying away toxins and debris

•2. clotting factors and complement proteins leave the
bloodstream enter the infected area
Clotting forms around the damages area , isolates the area and
slows the spread of the chemical/pathogen to the healthy
tissues.
Meanwhile, the bacterial cells wall is broken down by the
complement through the alternative pathway
3. Increased blood flow , elevates local temperature, rate of
the activity and accelerates phagocytic activity

4. Debris and bacteria are attacked by neutrophils drawn by
chemotaxis
As they circulate, neutrophil undergo activation:
-stick to the side of vessels and move in the tissue by
diapedesis
-increase their metabolic activity(rate),
“respiratory burst”
-they generate reactive compound such nitric oxide, hydrogen peroxide
peroxide
-secrete cytokines that attract other neutrophils and macrophages

5. Macrophages
Free and fixed macrophages engulf pathogens and cells debris
At first, macrophages are outnumbered by neutrophils
The number increases rapidly as secretion of cytokines continue
Eosinophils may get in if foreign material are coated by antibo
dies.
6. Other cytokines(released by active phagocytes)
stimulate fibroblasts ,to start barricading the area with scar, to
reinforce the clot and slow the invasion of adjacent.

7. Abnormal tissues and chemicals released by mast cells
stimulate local sensory neurons(pain)
8. Body’s specific defense
As inflammation progresses, the foreign proteins, toxins,
microorganisms and active phagocytes activate body’s specific
specific defense.

Symptomsof inflammationMechanism.
Rednessand Warmth(heat)
Ruborand Calor
Vasodilationof vessel, increase blow
Flow through tissues …to area
Swelling(Tumor) Chemicals released by mast cells
make the endothelial cells of local
capillaries more permeable ; blood,
proteins, plasma diffuse into the
injured tissue.
Pain(Dolor) Isthe result of abnormal tissue
conditions , stimulation of nerve
endings by chemicals released by
mast cells

Steps of the inflammatory response

•Fever
Fever : body temperature greater 37.2
0
C
Temperature is maintained constant by a center in the hypothalamus
(thermostat)
Feveris considered a nonspecific defense mechanism because it develops
in
response to numerous traumas.
Is initiated by some circulating proteins(Pyrogens) can reajust (reset) and
raise body temperature
Stimuli : ‘pathogens, bacteria toxins, Anti-B –Antigen complex

•Excessive fever can be dangerous, however fever is believed to have a
beneficial role because it retards the growth of temperature-sensitive
microorganisms (for example, leprosy bacilli), and it increases the
metabolism of body cells while stimulating the immune reaction and
the process of phagocytosis.

•IMMUNE EFFECTORS CELLS
There are many effector cells:
white blood cells
some precursor cells that eventually develop into the
mature cells of the tissue
Circulating immunologic cells include :
granulocytes( neutrophils, eosinophils, basophils), monocytes
and lymphocytes

•The immuno-response is further magnified by these cells and by
macrophages and mast cells

•Granulocytes
Their cytoplasm contains biologically active substances involved in
inflammation and allergic reaction
1.Neutrophils: ½ life 6hours . Hence need continuous production normal
circulating blood level: estimated 100 billions per day.
Mechanism action :
They are triggered by cytokines in the presence of infection or inflammation

•Many neutrophils enter the tissues,( if triggered by an infection or by
inflammatory cytokines).
oThey are attracted to the endothelial surface by cell adhesion molecules
selectins, and they roll along it.
oThey then bind firmly to neutrophil adhesion molecules of theintegrin
family
oThey next insinuate themselves by diapedesis through the walls of the
capillaries between endothelial cells .

•Neutrophils also discharge the enzyme myeloperoxidase (MPO) which
catalyzesthe conversion of Cl–, Br–, I–, and SCN–to the corresponding
acids (HOCl, HOBr, ..).
These acids are also potent oxidants.( reactive oxygen intermediate)
Because Cl–is present in greatest abundance in body fluids, the principal
product is HOCl( hypochlorous acid) which plays important role in the
microbial killing by neutrophils(Respiratory burst)

•Killing zone
Neutrophil granules contain also defensins elastase, metalloproteinases,
which attack collagen,
A variety other proteases help destroy invading organisms.
These enzymes act in a cooperative fashion with O2–, H2O2, and HOClto
produce a killing zone around the activated neutrophil.
This zone is effective in killing invading organisms, but in certain diseases
(eg, rheumatoid arthritis) the neutrophils may also cause local destruction
of host tissue.

•Eosinophils
They have a short half-life in the circulation, are attracted to the surface of
endothelial cells by selectins, bind to integrins that attach them to the vessel
wall, and enter the tissues by diapedesis.(like neutrophils)
•They release proteins, cytokines, and chemokines that produce inflammation
that are capable of killing invading organisms.
•They are selective in the way they respond and secrete killing molecules
•Maturation and activation in the tissue is stimulated by IL-3, IL-5, and
granulocyte-macrophage colony-stimulating factor (GM-CSF)

•They are especially abundant in the mucosa of the gastrointestinal
tract, where they defend against parasites, and in the mucosa of the
respiratory and urinary tracts

3. Basophils(BHH)
•Theyentertissuesandreleaseproteasesandcytokines.
•Theyresemblebutarenotidenticaltomastcells,andlikemastcellsthey
theyreleasehistamineandotherinflammatorymediatorswhen
activatedbybindingofspecificantigenstocell-fixedIgEmolecules,and
participateinimmediate-typehypersensitivity(allergic)reactions:mild
urticariaandrhinitisorsevereanaphylacticshock.
•TheantigensthattriggerIgEformationandbasophil(andmastcell)
activationareinnocuoustomostindividualsandarereferredtoas
allergens.

•Mast cells
•heavily granulated cells of the connective tissue.
•they are abundant in tissues that come into contact with the external
environment, such as beneath epithelial surfaces.
•Their granules contain proteoglycans, histamine, and many proteases. Like
basophils, they degranulate when allergens bind to cell-bound IgE
molecules directed against them.
•They are involved in inflammatory responses initiated by immuno-globulins
IgEand IgG
•They are involved in acquired immunity

•They release TNF-α in response to bacterial products by an antibody-
independent mechanism, thus participating in the nonspecific innate
immunitythat combats infections prior to the development of an
adaptive immune response
•Marked mast cell degranulation produces clinical manifestations of
allergy including anaphylaxis.

•Monocytes
•They enter the blood from the bone marrow and circulate for about 72 hrs . As they
then enter the tissues , they become tissue macrophages.
•Their life span in tissues is estimated to 3months
•Macrophages are activated by cytokines released from T lymphocytes,.
•Activated macrophages migrate in response to chemotactic stimuli and engulf and kill
bacteria by processes generally similar to those occurring in neutrophils.
•The play a key role in innate immunity .
•They secrete up to 100 different substances, including factors that affect lymphocytes
and other cells, prostaglandins of the E series, and clot-promoting factors.

lymphocytes
Lymphocytes are key elements in the production of acquired immunity
(see below).
Lymphocytes enter the bloodstream for the most part via the lymphatics.
Only about 2% of the body lymphocytes are in the peripheral blood.
Most of the rest are in the lymphoid organs.
In humans, 3.5 ×10
10
lymphocytes per day enter the circulation via the
thoracic duct alone; however, this count includes cells that re-enter the
lymphatics and thus traverse the thoracic duct more than once

•T and B lymphocytes are morphologically indistinguishable but can
be identified by markers on their cell membranes.
•B cells differentiate sequentially into cells capable of production of
various classes of immunoglobulins and thereafter enter plasma.

Hence memory cells are close to sites of reinfection and may account in part
for the rapidity and strength of their response.
Markers on the surface of lymphocytes are assigned CD (clusters of differen
tiation) numbers on the basis of their reactions to a panel of monoclonal
antibodies.
•Most cytotoxic T cells(T
C ) display the glycoprotein CD8, and helper T(T
H )
cells display the glycoprotein CD4
Note : Markers are glycoproteins

•Memory B cells and T cells
•After been exposed to a given antigen, a small number of activated B
and T cells persist as memory B and T cells.
•These cells are readily converted to effector cells by a later encounter
with the same antigen.
•In the event of a second exposure to same antigen the response , will
be fast accelerated response (key characteristic of acquired immunity)
•This ability persists for long periods of time, and in some instances (e.g,
immunity to measles) it can be life-long.

•After activation in lymph nodes, lymphocytes disperse throughout the
body and are especially abundant in areas where invading organisms
enter the body (eg, the mucosa of the respiratory and gastrointestinal
tracts).
•Chemokines are involved in guiding activated lymphocytes to these
locations.

•CYTOKINES
Cytokines are hormone-like molecules that act generally in a paracrine
fashion to regulate immune responses.
They are secreted not only by lymphocytes and macrophages but by
endothelial cells, neurons, glial cells, and other types of cells.

•Cytokines :Activate T cells division…memory T cells
Accelerate the maturation of cytotoxic cells
On macrophages : attract macrophages
prevent their departure
stimulate phagocytic activity and effectiveness
On NK cells : attract and stimulate
On B cells : promote activation, B cells maturation…
plasma cells maturation, production of antibodies

2
nd
line : innate immune cells
The cells that mediate innate immunity include :
neutrophils, macrophages, and NK cells.
All these cells respond to molecular patterns produced by bacteria and
to other substances characteristic of viruses, tumor, and transplant cells.
Many cells that are not immunocytes may nevertheless also contribute
to innate immune responses :
endothelial and epithelial cells.
The activated cells produce their effects via the release of cytokines,as
well as, in some cases, complement and other systems.

•ACQUIRED IMMUNNITY(adaptive/specific)
customer-made vs one-size-fits-all
•The key to acquired immunity is the ability of lymphocytes to produce
antibodies (in the case of B cells) or cell-surface receptors (in the case
of T cells) that are specific to one of the million of foreign antigens
•The antigens stimulating production of T cell receptors or antibodies
are usually proteins and poly peptides,
Antibodies can also be formed against nucleic acids and lipidsif these
are presented as nucleoproteins and lipoproteins.

•Acquired immunity has two components:
humoral immunity and cellular immunity
Humoral immunity is mediated by circulating immunoglobulin antibodies in the γ-
globulin fraction of the plasma proteins.
Immunoglobulins are produced by differentiated forms of B lymphocytes : plasma
cells.
They activate the complement system and attack and neutralize antigens.
Humoral immunity is a major defenseagainst bacterial infections.

•Cellular immunity is mediated by T lymphocytes.
•It is responsible for delayed allergic reactions and rejection of
transplants of foreign tissue.
•Cytotoxic T cells attack and destroy cells bearing the antigen that
activated them.
•They kill by inserting perforins and by initiating apoptosis.
•Cellular immunity a major defenseagainst infections due to viruses,
fungi, and a few bacteria such as the tubercle bacillus. It also helps
defend against tumors.

Cell-mediated immunity
•Mechanisms : Cells, course of events
•Cells : T cells(3)
1.Cytotoxic T cells (T
C): responsible for cell-mediated immunity
Enter peripheral tissue:
attack antigen: physically or chemically
2.Helper T cells(T
H): Stimulate T cells and B cells response.
3. Suppressor T Cells(T
S) :Moderate immunity by suppressing T cells and B
cells activity

Helper T cells
•Most numerous of T cells
•Help in the functions of the immune system
•Major regulator of all immune functions by forming lymphokines(proteins
mediators) : act on other cells
act on bone marrow
Lymphokines secreted: Interleukin ,2,3,4,5,6
Granulocyte-monocyte colony stimulating factor
Interleukin-gamma

•Some functions of lymphokins
•Stimulation of growth and proliferation of Cytotoxic T cells and
Suppressor T cells
•Stimulation of B-cell growth and differentiation ..plasma
cells..antibodies
•Activation of macrophage-monocyte system
•Feedback, stimulation effect on the helper cells.

•Antigen presentation : APC
•The number of different antigens recognized by lymphocytes in the body is
extremely large. The repertoire develops initially without exposure to the
antigen.
•Stem cells differentiate into many million different T and B lymphocytes, each
with the ability to respond to a particular antigen
•In case of T cells , the antigen is taken up by an antigen-presenting cell (APC) and
partially digested
Tc recognize antigen when bound to glycoprotein on the cell membrane
•The process of antigen presentation occurs when the antigen-glycoprotein
complex capable of activating T cells appears in the membrane.

•APC : specialized cells that activate T cells defense against
• foreign cells(bacteria) and foreign protein
•APC : All phagocytic cells of Monocytes-macrophage group
Free and fixed macrophages
Kupffer cells of the liver
Microglia in the CNS
Langerhans cells of the skin
dendritic cells of the lymph nodes and of the spleen

•In APCs, polypeptide products of antigen digestion are coupled to the
major histocompatibility complex (MHC) genes and presented on the
surface of the cell.
MHC is a collection of gene located on chromosome 6.
It is organized into 3 classes regions

Markers on the surface of lymphocytes are assigned CD (clusters of
differentiation) numbers on the basis of their reactions to a panel of
monoclonal antibodies.
Most cytotoxic T cells(T
C ) display the glycoprotein CD8, and helper T(T
H )
cells display the glycoprotein CD4
Note : Markers are glycoproteins
CD markers are membrane proteins
CD : Cluster of differentiation

CD : Cluster of differentiation
Cluster of Designation
Classification Determinant
CD is a way/protocol used for identification and investigation of cell surface
molecules providing targets for immunophenotypes of cells(leucocytes)
CD4 :
Thymocytes subtypes, T-Helper cells, Regulatory T-cells, monocytes and
macrophages

•Class I :
encode for glycoproteins expressed on the surface of nearly every nucleated cells
in the bodyTheseproteins are called MHC class I receptors . They present antigen
to CD8+ T
Class II :
encodes for glycoproteins expressed only on the surface of APC and lymphocytes
These proteins are called MHC class II receptors. They present antigen to CD4+ T
cells
These proteins: MHC proteins( I&II)are also called or human leucocytes
antigens(HLAs)

•Antigen recognition
Recognition :
CD4(helper) and CD8 T cell surface molecules play a role in T cell recognition and activation by binding to
their respective class II and class I major histocompatibility complex (MHC) ligands on an antigen
presenting cell (APC)
T-cells can’t recognize antigen unless it is presented to them by MHC receptors
Helper CD4+ cells recognize and respond to antigen only when they are presented to them by
MHC receptors class II
Cytotoxic CD8+ T cells recognize and respond to antigen only when they are presented to them
by MHC receptors class i
I

CD4 functions : T-cells activation,
Thymicdifferentiation
Receptors of HIV
CD8 : thymocytessubtypes
Cytotoxic T-cells
Natural killers
Dentriticcells subtypes
Function : receptors for MHC class I molecule

•Two classes of MHC
•Class I MHC:
•an antigen bound to the MHC, send a signal: abnormal cells
•Location : membrane of nucleated cells
•Continuously being synthetized and exported to the Golgi apparatus and
pick up small peptides as they form
If the cell is healthy and peptides are normal: T cells ignore them
If abnormal protein or viral(non self) in the cytoplasm, T cells are activated and
destroy the abnormal cells.
Eg.:Rejection of transplanted tissue as foreign
•

•Class II MHC: only present in the membrane of APC and lymphocytes
•APCs engulf and break down pathogens of foreign antigen.( antigen
processing)
•Breaking down creates antigen fragments, which will then bind to
class II MHC.

•CD8 /DC4 markers are bound to CD3 complex
•CD3 activate T cell
Costimulation
Prior the activation the T cell bind to a stimulating cell which
promote the transcription(at the nucleus) , division and
differentiation
•Costimulation helps to determine whether the cell will be
activated

•Activation of CD8 T cells(2 types are activated)
•One type of CD8 respond quickly resulting in larger number of
cytotoxic T Cells and memory Tcells
•Second type :Slow response …give rise to a small number of
suppressor cells
•Cytotoxic T cells: Tc cells or Killers T cells
•Action : seek and destroy abnormal cells
highly mobile cells
bind to class I MHC proteins

•Mechanism of destruction of target cells
•Perforinsreleased destroy the antigen cell membrane
•Lymphotoxins, which poison kill the target cell
•Apoptosis: Killer T cells active genes in the target cell nucleus
…message ..die

•Memory Tc cells
Role : to ensure that when comes the second exposure to the same
antigen there will be no delay in the response
During the second appearance of the same antigen, memory cells differentiate
into cytotoxic T cells , with swift , effective response, overtaking the capability of
the invading organism.

•Suppressor T cells( TsCells):
•Suppress the responses of other T cells and B cells by secreting
suppressing factors
•Activation of CD4 T cells
•CD4 activation : series of division …helper T cells( T
Hcells) and
memory T
Hcells
•Memory T
Hcells remain in reserve
•Helper T cells secrete cytokines

Humoral immunity
( B cells and antibodies mediated )
Step I : Sensitization of B cells
The membrane of each kind of B cell carries its own antibody
molecules.
They bind to the corresponding antigen when it appears in the
interstitial fluid(sensitization)
Step II : help from helper T cells …activation
T
Hcells bind to MHC (recognize the antigen) then secretion of
cytokines… B cells activation

•Cytokines …stimulate B cells : division and maturation of plasma cells
•production of antibodies

•ANTIBODIES (IMMUNOGLOBULINS)
•Antibodies protect their host by:
1. binding to and neutralizing some protein toxins,
2. by blocking the attachment of some viruses and bacteria to cells, by
opsonizing bacteria ,
3. by activating complement.

•Antibody structure
•Consists of 2 parallel pairs of polypeptide chains(heavy and
light)
•Each chain has constant and variable segments
constant segment : base of the antibody

•Antibodies fragment:
Antibody fragment can be : a fragment antigen-binding (Fab)
a fragment crystallizable(Fc)

•The heavy-chain , bound to constant segment of light chain contain
bindings sites that can activate the complement system.

The classification of antibodies is based on the type of the constant segment
The structure of the the heavy chain determines the way the antibody is
produced and how it is distributed in the body.
( some circulate in the body fluids, other bind to the membrane of mast cells
and basophils)
The B cells produce only 5 types
Human body( normal) :
roughly 10 trillion B cells
B cells can produce an estimated 100 million AB

•Differences in heavy chain polypeptides allow these immunoglobulins
to function in different types of immune responses and at particular
stages of the immune response.
•The polypeptide protein sequences responsible for these differences
are found primarily in the Fc fragment.
•While there are five different types of heavy chains, there are only
two main types of light chains: kappa (κ) and lambda (λ).

•Antibody classes differ in valency as a result of different numbers of
Y-like units (monomers) that join to form the complete protein.
•For example, in humans, functioning IgM antibodies have five Y-
shaped units (pentamer) containing a total of ten light chains, ten
heavy chains and ten antigen-binding sites

•General functions antibodies
a. antigen-binding
antibodies bind specifically to one or few closely related antigen.
Each antibody binds to a specific antigen determinant
b. Effector function
Fixation of complement which leads to lyse of cells and the release of
biologically active molecules.
Binding to various cells types : phagocytes, lymphocytes, platelets, mast
cells, basophils

•The five primary classes of immunoglobulins(antibodies) are IgG, IgM,
IgA, IgDand IgE. They are distinguished by the type of heavy chain
found in the molecule.
IgG molecules have heavy chains known as gamma-
chains;
IgMshave mu-chains;
IgAshave alpha-chains;
IgEshave epsilon-chains; and
IgDshave delta-chains.

•The Antigen-Antibody complex
•Antigen-antibody is formed when the antibody bonds to the
corresponding antigen( then H bonding and other forces lock)
•Area of antibody binding on the antigen : Antigenic determinant sites

Antigen-antibody complex ways of eliminating the antigen
1.Neutralization
antibodies may bind to the specific regions for cells binding
By binding the area antibodies make virus, toxin, viruses
incapable to attach to the cell.
2. Agglutination and Precipitation
It is when an antibody binds antigenic determinant sites on 2
antigens(closer)
Antibodies can form a bridges that tie a great number of antigens

3.Precipitation:
•When the antigen is a soluble molecule, the formed can be
large to remain in the solution .
The formation of an immune complex(insoluble): Precipitation
Agglutination : formation of large immune complex at the surface
of a cell or virus.
4. Activation of the complement(see complement activation)

•5.Attraction of phagocytes
Antigen coated with antibodies attract eosinophils, neutrophils
,and macrophages.( destroy foreign cells or abnormal cell
membrane)
5.Opsonization
6. Stimulation of inflammation
antibodies can stimulate basophils and mast cells
7. Prevention of bacterial and viral adhesion
Antibodies dissolved in the saliva, mucus

Classes of antibodies: structure and function
•IgG : largest and most diverse class
80% of all antibodies
half life : 7-23 days
Monomer of epitopes binding sites
Functions:
resistance against many viruses, bacteria, bacterial toxins
Provide passive immunity to fetus from the mother
The only class of Ig that cross the placenta and enter the fetus
Note: anti-Rh antibodies are IgG(HDN)

IgE: 13% , half life : 5 days
attach to the exposed surface of basophils and mast cells
when a corresponding antigen binds IgE…stimulate the
release of histamine and accelerate inflammation(area)
Role in allergic reaction
•IgD: attached as an individual molecule at the surface of B
cells . Bind antigen in the extracellular fluid.
Role : activation of B cells

•IgM : 13 %
•First antibodies secreted , half life : 5days
•First Ig class produced , with primary response to antigen
Production decline as IgG production accelerates
May attack bacteria that are insensitive to IgG
•Activation of the classical
Pathway
•Act as opsonin

Produced as an individual molecule, but circulate in a
configuration of five antibodies starburst(base units)
particularly effective
in forming immune
complex
Note: Anti-A antibodies & anti-B
antibodies for agglutination
blood are IgM

IgA : 6% , half life : 5 days
Dimer of 4 epitopes binding sites
•glandular secretion mucus, tear,
saliva
Circulate as individual or pair
Attack pathogens before they gain
access to internal tissues
Absorbed by epithelial cells from
periphery and attach the secretory
piece(yellow)
Effective against virus causing influenza

Humoral immune response:
primary and secondary response
Humoral response can be differentiated into Primary and Secondary
response
•Primary response
The primary immune response of the body to the Ag occurs on the first
occasion when it is encountered
Depending on the site and the type of the Ag, the primary response
can take 2, 3 up to 14 days and leads to the generation of memory cells
with high specificity for the inducing antigen.

The humoral response mediated by B cells with help of T cells produces high affinity
and antigen-specific antibodies.
Secondary response
•Following response is observed following subsequent encounter with the same
antigen and is more rapid ,leading to the activation of previously generated
memory cells
•In a secondary response to the same antigen, memory cells are rapidly activated.
•This process is quicker and more effective than the primary response.

BLOOD AND BLOOD COMPONENT- introduction to blood physiology

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BLOOD AND BLOOD COMPONENT- introduction to blood physiology

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