701350948-01Intro-and-Innate-Immunity-1.ppt

Microbiology immune

1. HNS204 IMMUNOLOGYHNS204 IMMUNOLOGY
DR. K. MARITIMDR. K. MARITIM

2. What is Immunology?What is Immunology?
Immunology is the biochemical study of body defences Immunology is the biochemical study of body defences
againstagainst

bacteria, bacteria,

virus, virus,

fungi and fungi and

parasites.parasites.

3. 
Basic Immunology involves the understanding of Basic Immunology involves the understanding of
physiochemical properties of substances physiochemical properties of substances
(immunochemistry), at level of molecules (immunochemistry), at level of molecules
(molecular immunology), cells (cellular (molecular immunology), cells (cellular
immunology ) immunology )

Clinical Immunology deals with various immune Clinical Immunology deals with various immune
mediated diseases including reproductive, mediated diseases including reproductive,
hematological (immunohaematology), hematological (immunohaematology),
immunodeficiency, infection and immunity, immunodeficiency, infection and immunity,
tumours, graft rejections (clinical transplantation), tumours, graft rejections (clinical transplantation),
allergic, hypersensitivity and autoimmune allergic, hypersensitivity and autoimmune
associated disorders.associated disorders.

4. 
Immunology is of major value in many areas ofImmunology is of major value in many areas of
biomedical, clinical, dentistry, pharmacy and basic biomedical, clinical, dentistry, pharmacy and basic
sciences.sciences.

In disease diagnosis , immunodiagnostics provide In disease diagnosis , immunodiagnostics provide
useful data in treatment and management useful data in treatment and management
including perspectives on underlying including perspectives on underlying
mechanisms within a disease process.mechanisms within a disease process.

Confronting challenges of emerging diseases Confronting challenges of emerging diseases
requires better tooling in immune based requires better tooling in immune based
therapies including gene therapy, phototherapy, therapies including gene therapy, phototherapy,
use of cytokines and adoptive cell transfer.use of cytokines and adoptive cell transfer.

5. 
Immunotherapeutical vaccines are also Immunotherapeutical vaccines are also
important in the control of many diseases important in the control of many diseases
particularly conventional vaccines against particularly conventional vaccines against
viral and bacterial infections. viral and bacterial infections.

Furthermore, Immunology is important in Furthermore, Immunology is important in
several other fronts like anthropological several other fronts like anthropological
studies, paternity identity and criminal studies, paternity identity and criminal
identification through the employment of identification through the employment of
DNA and HLA characterization.DNA and HLA characterization.

6. HISTORICAL PERSPECTIVESHISTORICAL PERSPECTIVES

Scientist(s)---ContributionScientist(s)---Contribution

Edward Jenner (1749 – 1823)--Experimented with cowpox Edward Jenner (1749 – 1823)--Experimented with cowpox
leading to small pox vaccine in 1796leading to small pox vaccine in 1796

Louis Pasteur (1822)--Introduced vaccine with the first Louis Pasteur (1822)--Introduced vaccine with the first
attenuated virus vaccine.attenuated virus vaccine.

Pasteur (1881 – 1885)--Germ theory led to production of Pasteur (1881 – 1885)--Germ theory led to production of
attenuated vaccines against anthrax, cholera and rabies.attenuated vaccines against anthrax, cholera and rabies.

Ilya Metchnikoff (1845 – 1916)Ilya Metchnikoff (1845 – 1916)
--Proposed “cellular theory of immunity” involving --Proposed “cellular theory of immunity” involving
“phagocytosis” of “wondering” cells (1884).“phagocytosis” of “wondering” cells (1884).

7. 
Paul Ehrlich (1854 – 1915 --Believed “humoral Paul Ehrlich (1854 – 1915 --Believed “humoral
immunity” involving antibodies and not cells.immunity” involving antibodies and not cells.

Wright and Douglas (1903)Wright and Douglas (1903)
--Demonstrated enhancement of phagocytosis --Demonstrated enhancement of phagocytosis
by serum opsonins indicating a linkage by serum opsonins indicating a linkage
between humoral and cellular immunity.between humoral and cellular immunity.

Von Behring (1854-1917) and Kitasato (1870)Von Behring (1854-1917) and Kitasato (1870)
--First described diphtheria antitoxin (antibody) --First described diphtheria antitoxin (antibody)
– (1890).– (1890).

8. 
Robert Koch (1843-1910)Robert Koch (1843-1910)
--Described delayed hypersensitivity reaction to --Described delayed hypersensitivity reaction to
tuberculin (Koch’s phenomenon).tuberculin (Koch’s phenomenon).

Buchner (1893)--Described a heat labile Buchner (1893)--Described a heat labile
serum factor (complement)serum factor (complement)

Bordet (1895) --Demonstrated bacteriolysis of Bordet (1895) --Demonstrated bacteriolysis of
CCholera vibrioholera vibrio by antibody and complement. by antibody and complement.

9. 
Ehrlich (1897)Ehrlich (1897) --Proposed receptor theory of --Proposed receptor theory of
antibody synthesis and first described antibody synthesis and first described
neutrophils and eosinophils.neutrophils and eosinophils.

Landsteiner (1900)--Discovered human ABO Landsteiner (1900)--Discovered human ABO
blood group systemblood group system

Von Pirquet (1874-1929) --Described serum Von Pirquet (1874-1929) --Described serum
sicknesssickness

Fleming (1922)Fleming (1922) --Identified lysozymes--Identified lysozymes

Tiselius and Kobet (1938)Tiselius and Kobet (1938) --Demonstrated that --Demonstrated that
antibody activity resided in the gamma antibody activity resided in the gamma
globulin portion of serum proteins.globulin portion of serum proteins.

10. 
Paul Ehrlich (1892)Paul Ehrlich (1892) --Showed maternal transfer --Showed maternal transfer
of species specific immunity to infant through of species specific immunity to infant through
milk.milk.

Calmette Guerrin (1920) --Developed avirulent Calmette Guerrin (1920) --Developed avirulent
BCG vaccine.BCG vaccine.

Colonel Ogden Bruton (1952)Colonel Ogden Bruton (1952) -- --Found Found
agammaglobulinaemia in a male child.agammaglobulinaemia in a male child.

Glick and Change (1956)Glick and Change (1956) -- --Observed that Observed that
antibody production in chicken dependent on antibody production in chicken dependent on
the presence of the Bursa of Fabricius in birdsthe presence of the Bursa of Fabricius in birds

11. 
Henson (1739-1774) --Described lymphocytes and Henson (1739-1774) --Described lymphocytes and
were stained and studied by Paul Ehrlich (1879).were stained and studied by Paul Ehrlich (1879).

Holmes et al (1966) Holmes et al (1966) ----Described phagocytic defect, Described phagocytic defect,
chronic granulomatosis disease, in children.chronic granulomatosis disease, in children.

Doherty and Zinkernagel (1974)Doherty and Zinkernagel (1974)----Demonstrated Demonstrated
that T cell recognition of antigen was self –MHC that T cell recognition of antigen was self –MHC
restricted (1996).restricted (1996).

Susumu Tonegawa (1976)Susumu Tonegawa (1976)----Discovered that single Discovered that single
immunoglobulin proteins were encoded by immunoglobulin proteins were encoded by
separate rearranging genes (1987).separate rearranging genes (1987).

12. 
Kohler and Milstein (1975)Kohler and Milstein (1975)----Discovered the Discovered the
principle for production of monoclonal principle for production of monoclonal
antibodiesantibodies

Porter (1950s and 1960s)Porter (1950s and 1960s)----Showed Showed
immunoglobulins were composed of two immunoglobulins were composed of two
heavy and two light chains covalently bonded heavy and two light chains covalently bonded
(1950).(1950).

Max Theiler (1938)Max Theiler (1938)----Contributed to Contributed to
development of yellow fever vaccinedevelopment of yellow fever vaccine

13. What is immunity?What is immunity?

““Protection” from infection, tumors, etc.Protection” from infection, tumors, etc.

Innate immunity is always availableInnate immunity is always available

Adaptive immunity distinguishes “self” from Adaptive immunity distinguishes “self” from
“non-self” and involves immune system “non-self” and involves immune system
“education”“education”

Responses that may result in host tissue Responses that may result in host tissue
damagedamage

Defence mechanisms evolved from innate Defence mechanisms evolved from innate
immunity involving mainly the skin and immunity involving mainly the skin and
mucous to two arms of immune system, mucous to two arms of immune system,
humoral and cellular responses.humoral and cellular responses.

14. CLASSIFICATION OF IMMUNE CLASSIFICATION OF IMMUNE
RESPONSESRESPONSES

Innate immunity (not antigen-specific)Innate immunity (not antigen-specific)

Anatomical barriersAnatomical barriers

MechanicalMechanical

BiochemicalBiochemical

Non-specific (eg. Low pH in stomach)Non-specific (eg. Low pH in stomach)

Receptor-driven (eg. PAMP-recognition)Receptor-driven (eg. PAMP-recognition)

Adaptive immunity (antigen-specific)Adaptive immunity (antigen-specific)

Receptor-drivenReceptor-driven

Pre-existing clones programmed to make a specific Pre-existing clones programmed to make a specific
immune response (humoral/cellular)immune response (humoral/cellular)

15. AntigenAntigen

A substance (antigen) that is capable of A substance (antigen) that is capable of
reactingreacting with the products of a specific with the products of a specific
immune response, e.g., antibody or specific immune response, e.g., antibody or specific
sensitized T-lymphocytes.sensitized T-lymphocytes.

A “self” component may be considered an A “self” component may be considered an
antigen even though one does not generally antigen even though one does not generally
make immune responses against those make immune responses against those
components.components.

16. Characteristics of Adaptive Characteristics of Adaptive
ImmunityImmunity

Immune response is highly specific for the antigen that Immune response is highly specific for the antigen that
triggered it.triggered it.

Receptors on surface of immune cells have same specificity as the Receptors on surface of immune cells have same specificity as the
antibody/effector activity that will be generatedantibody/effector activity that will be generated

Exposure to antigen creates an immunologic “memory.”Exposure to antigen creates an immunologic “memory.”

Due to clonal expansion and creation of a large pool of cells committed Due to clonal expansion and creation of a large pool of cells committed
to that antigento that antigen

Subsequent exposure to the same antigen results in a rapid and Subsequent exposure to the same antigen results in a rapid and
vigorous responsevigorous response

17. Components of the Components of the
immune systemimmune system

18. Cells Cells
involved involved
in in
immunityimmunity
platelets platelets
megakaryocyte megakaryocyte
eosinophil eosinophil
neutrophil neutrophil
basophil basophil
mast cell mast cell
common common
myeloid myeloid
progenitor progenitor
monocyte monocyte
macrophage macrophage
NaturalNatural
Killer cellKiller cell
plasma cell plasma cell
B LymphocyteB Lymphocyte
T LymphocyteT Lymphocyte

common common
lymphoid lymphoid
progenitor progenitor
Pluripotent Pluripotent
hematopoietichematopoietic
stem cellstem cell

19. BloodBlood
Serum or Serum or
PlasmaPlasma
Leukocytes, Leukocytes,
Platelets and RBCPlatelets and RBC
Serum ProteinsSerum Proteins
Mononuclear Mononuclear
CellsCells
Polymorphonuclear Polymorphonuclear
leukocytes (or leukocytes (or
Granulocytes)Granulocytes)
•
ImmunoglobulinsImmunoglobulins
•
ComplementComplement
•
Clotting factorsClotting factors
•
Many othersMany others
•
NeutrophilsNeutrophils
•
EosinophilsEosinophils
•
BasophilsBasophils
•
Lymphocytes Lymphocytes
(T cells, B cells (T cells, B cells
& NK cells)& NK cells)
•
MonocytesMonocytes
Where is that stuff?Where is that stuff?

20. Lymphoid OrgansLymphoid Organs

Primary or central lymphoid organsPrimary or central lymphoid organs

bone marrow and thymusbone marrow and thymus

where lymphocytes are generatedwhere lymphocytes are generated

Secondary or peripheral lymphoid organsSecondary or peripheral lymphoid organs

where adaptive immune responses are initiatedwhere adaptive immune responses are initiated

21. Distribution of Lymphoid TissuesDistribution of Lymphoid Tissues

22. Response to Initial Infection Response to Initial Infection

23. Stages of Response to InfectionStages of Response to Infection

24. Course Course
of of
Typical Typical
Acute Acute
InfectionInfection

25. Innate Host Defense MechanismsInnate Host Defense Mechanisms

Genetic determinantsGenetic determinants

Anatomic FactorsAnatomic Factors

Mechanical FactorsMechanical Factors

Biochemical FactorsBiochemical Factors

26. SkinSkin

Stratified and cornified epithelium provides a Stratified and cornified epithelium provides a
mechanical barriermechanical barrier

Indigenous microbiota competes with pathogensIndigenous microbiota competes with pathogens

Acid pH inhibits growth of disease producing Acid pH inhibits growth of disease producing
bacteriabacteria

Bactericidal long chain fatty acids in sebaceous Bactericidal long chain fatty acids in sebaceous
gland secretionsgland secretions

27. Respiratory TractRespiratory Tract

Upper Respiratory TractUpper Respiratory Tract

Nasal hairs induce turbulenceNasal hairs induce turbulence

Mucous secretions trap particlesMucous secretions trap particles

Mucous stream to the base of tongue where material is swallowedMucous stream to the base of tongue where material is swallowed

Nasal secretions contain antimicrobial substancesNasal secretions contain antimicrobial substances

Upper respiratory tract contains large resident floraUpper respiratory tract contains large resident flora

Lower Respiratory TractLower Respiratory Tract

Particles trapped on mucous membranes of bronchi and bronchiolesParticles trapped on mucous membranes of bronchi and bronchioles

Beating action of cilia causes mucociliary stream to flow up into the pharynx Beating action of cilia causes mucociliary stream to flow up into the pharynx
where it is swallowedwhere it is swallowed

90% of particles removed this way. Only smallest particles (<10µ in diameter) 90% of particles removed this way. Only smallest particles (<10µ in diameter)
reach alveolireach alveoli

AlveoliAlveoli

Alveolar macrophage rapidly phagocytize small particlesAlveolar macrophage rapidly phagocytize small particles

28. Alimentary TractAlimentary Tract

General defense mechanismsGeneral defense mechanisms

Mucous secretionsMucous secretions

Integrity of of mucosal epitheliumIntegrity of of mucosal epithelium

Peristaltic motions of the gut propel contents downwardPeristaltic motions of the gut propel contents downward

Secretory antibody and phagocytic cellsSecretory antibody and phagocytic cells

StomachStomach

Generally sterile due to low pHGenerally sterile due to low pH

Small IntestineSmall Intestine

Upper portion contains few bacteriaUpper portion contains few bacteria

As distal end of ilieum is reached flora increasesAs distal end of ilieum is reached flora increases

ColonColon

Enormous numbers of microorganismsEnormous numbers of microorganisms

50-60% of fecal dry weight is bacteria50-60% of fecal dry weight is bacteria

29. Genitourinary TractGenitourinary Tract

MaleMale

No bacteria above urethrovesicular junctionNo bacteria above urethrovesicular junction

Frequent flushing action of urineFrequent flushing action of urine

Bactericidal substances from prostatic fluidBactericidal substances from prostatic fluid

pH of urinepH of urine

Bladder mucosal cells may be phagocyticBladder mucosal cells may be phagocytic

Urinary sIgAUrinary sIgA

Female (Vagina)Female (Vagina)

Large microbial population (lactobacilli)Large microbial population (lactobacilli)

Microorganisms produce low pH due to breakdown of glycogen produced by Microorganisms produce low pH due to breakdown of glycogen produced by
mucosal cellsmucosal cells

30. EyeEye

Flushing action of tears which drain through the Flushing action of tears which drain through the
lacrimal duct and deposit bacteria in nasopharynxlacrimal duct and deposit bacteria in nasopharynx

Tears contain a high concentration of lysozyme Tears contain a high concentration of lysozyme
(effective against gram positive microorganisms(effective against gram positive microorganisms

31. ReceptorsReceptors

Almost all of biology occurs because Almost all of biology occurs because
recognitionrecognition

Enzymatic actionEnzymatic action

Interactions between cells Interactions between cells
(cooperation/activation)(cooperation/activation)

Communication between cellsCommunication between cells

Innate and adaptive immunity requires itInnate and adaptive immunity requires it

32. Innate Immune RecognitionInnate Immune Recognition

All multi-cellular organisms are able to All multi-cellular organisms are able to
recognize and eliminate pathogensrecognize and eliminate pathogens

Despite their extreme heterogeneity, Despite their extreme heterogeneity,
pathogens share highly conserved molecules, pathogens share highly conserved molecules,
called “pathogen-associated molecular called “pathogen-associated molecular
patterns” (patterns” (PAMPsPAMPs))

Host cells do not share PAMPs with pathogensHost cells do not share PAMPs with pathogens

PAMPs are recognized by innate immune PAMPs are recognized by innate immune
recognition receptors called pattern-recognition receptors called pattern-
recognition molecules/receptors (recognition molecules/receptors (PRMs/PRRsPRMs/PRRs))

33. Typical PAMPsTypical PAMPs

Lipopolysaccharides-found in g-ve bacteriaLipopolysaccharides-found in g-ve bacteria

Peptidoglycans---g+ve bacteriaPeptidoglycans---g+ve bacteria

Certain nucleotide sequences unique to Certain nucleotide sequences unique to
bacteriabacteria

Other bacterial componentsOther bacterial components

Ds RNA, ssRNADs RNA, ssRNA

Fungal glucansFungal glucans

34. Endogenous Signals Induced by PAMPsEndogenous Signals Induced by PAMPs

Mediate inflammatory cytokinesMediate inflammatory cytokines

Antigen-presenting cells recognize Antigen-presenting cells recognize
PAMPsPAMPs

Same APC processes pathogens into specific Same APC processes pathogens into specific
pathogen-derived antigens and presents them pathogen-derived antigens and presents them
with MHC encoded receptors to T-cellswith MHC encoded receptors to T-cells

T-cell responds only when presented with both T-cell responds only when presented with both
signalssignals

Different Effector Cytokines in Response to Different Different Effector Cytokines in Response to Different
Pathogens (Th1 vs. Th2)Pathogens (Th1 vs. Th2)

35. Antimicrobial Peptides/DefensinsAntimicrobial Peptides/Defensins

Four hundred peptides described to dateFour hundred peptides described to date

Defensins (3- 5-kD, four families in eukaryotes)Defensins (3- 5-kD, four families in eukaryotes)

-defensins (neutrophils and intestinal Paneth cells)-defensins (neutrophils and intestinal Paneth cells)

-defensins (epithelial cells)-defensins (epithelial cells)

Insect defensinsInsect defensins

Plant defensinsPlant defensins

Defensins appear to act by binding to outer Defensins appear to act by binding to outer
membrane of bacteria, resulting in increased membrane of bacteria, resulting in increased
membrane permeability.membrane permeability.

May also play a role in inflammation and wound May also play a role in inflammation and wound
repairrepair

36. Complement SystemComplement System

Three pathways now knownThree pathways now known

ClassicalClassical

AlternativeAlternative

Lectin or MBL pathway (binding to mannose-Lectin or MBL pathway (binding to mannose-
containing carbohydrates)containing carbohydrates)

Host cells have complement regulatory Host cells have complement regulatory
proteins on their surface that protect them proteins on their surface that protect them
from spontaneous activation of C3 moleculesfrom spontaneous activation of C3 molecules

37. Inflammatory Mediators in Innate Inflammatory Mediators in Innate
ImmunityImmunity

Cytokines secreted by phagocytes in response to infection Cytokines secreted by phagocytes in response to infection
include:include:

IL-1 IL-1

activates vascular endothelium and lymphocytesactivates vascular endothelium and lymphocytes

Increases adhesiveness of leukocytesIncreases adhesiveness of leukocytes

IL-6IL-6

Induces B-cell terminal maturation into Ig-producing plasma cellsInduces B-cell terminal maturation into Ig-producing plasma cells

IL-8IL-8

Induces expression of b2 integrin adhesion molecules on neutrophils, Induces expression of b2 integrin adhesion molecules on neutrophils,
leading to neutrophil migration to infection siteleading to neutrophil migration to infection site

IL-12IL-12

Activates NK cells and induces Th1-cell differentiationActivates NK cells and induces Th1-cell differentiation

IL-18IL-18

TNF-TNF-

Activates vascular endothelium and increases vascular permeability, Activates vascular endothelium and increases vascular permeability,
leading to accumulation of Ig and complement in infected tissuesleading to accumulation of Ig and complement in infected tissues

38. Other Mediators and MoleculesOther Mediators and Molecules

PhagocytesPhagocytes

Toxic oxygen radicalsToxic oxygen radicals

PeroxidesPeroxides

Nitric oxide (NO)Nitric oxide (NO)

Lipid mediators of inflammationLipid mediators of inflammation

ProstaglandinsProstaglandins

LTB4LTB4

Platelet activating factorPlatelet activating factor

Complement component C5aComplement component C5a

Stimulates mast cells to release histamine, serotonin and LTB4Stimulates mast cells to release histamine, serotonin and LTB4

IL-1, IL-6 and TNF-IL-1, IL-6 and TNF-

Induce acute-phase response in liverInduce acute-phase response in liver

Induce feverInduce fever

IL-1 and IL-18 signaling pathways activate NF-IL-1 and IL-18 signaling pathways activate NF-B, important in innate B, important in innate
immunityimmunity

39. Immune Cells and Innate ImmunityImmune Cells and Innate Immunity

PhagocytesPhagocytes

NeutrophilsNeutrophils

Monocyte/macrophageMonocyte/macrophage

Eosinophils (to a lesser extent)Eosinophils (to a lesser extent)

NK cells NK cells (large granular lymphocytes)(large granular lymphocytes)

Antibody-dependent cell-mediated cytotoxicity Antibody-dependent cell-mediated cytotoxicity
(ADCC)(ADCC)

Have two major functionsHave two major functions

Lysis of target cellsLysis of target cells

Production of cytokines (IFN-Production of cytokines (IFN- and TNF- and TNF-))

Act against intracellular pathogensAct against intracellular pathogens

HerpesvirusesHerpesviruses

LeishmaniaLeishmania

Listeria monocytogenesListeria monocytogenes

Act against protozoaAct against protozoa

ToxoplasmaToxoplasma

TrypanasomaTrypanasoma

40. Immune Cells and Innate Immune Cells and Innate
Immunity (cont’d)Immunity (cont’d)

g/d T cellsg/d T cells

Two types of T cell receptorsTwo types of T cell receptors

One composed of a and b chains (basic T cell antigen receptor)One composed of a and b chains (basic T cell antigen receptor)

One composed of g and d chains (minor population of T cells)One composed of g and d chains (minor population of T cells)

Two groups of g/d T cellsTwo groups of g/d T cells

One group found in lymphoid tissuesOne group found in lymphoid tissues

One group located in paracellular space between epithelial cellsOne group located in paracellular space between epithelial cells

Recognizes unprocessed target antigen in absence of APC helpRecognizes unprocessed target antigen in absence of APC help

B-1 cells (minor fraction of B cells, do not require T-cell help)B-1 cells (minor fraction of B cells, do not require T-cell help)

Mast cellsMast cells

Located in serosa, under epithelial surfaces and adjacent to blood vessels, nerves and glandsLocated in serosa, under epithelial surfaces and adjacent to blood vessels, nerves and glands

Capable of phagocytosisCapable of phagocytosis

Process and present antigen using MHC class I or II receptorsProcess and present antigen using MHC class I or II receptors

LPS can directly induce release of mast cell mediatorsLPS can directly induce release of mast cell mediators

Complement (C3a and C5a) induce mast cells to release mediatorsComplement (C3a and C5a) induce mast cells to release mediators

Chemotaxis, complement activation, inflammationChemotaxis, complement activation, inflammation

TNF-a secreted by mast cells results in neutrophil influx into infected siteTNF-a secreted by mast cells results in neutrophil influx into infected site

41. Summary of Innate ImmunitySummary of Innate Immunity

External and mechanical barriersExternal and mechanical barriers

Receptors for pathogen motifsReceptors for pathogen motifs

Soluble antimicrobial proteinsSoluble antimicrobial proteins

Pattern of cytokines produced Pattern of cytokines produced
influences adaptive responseinfluences adaptive response

42. TERMINOLOGIESTERMINOLOGIES

Antibody (AB): Antibody (AB): A protein produced as a A protein produced as a
result of interaction with an antigen. The result of interaction with an antigen. The
protein has the ability to combine with the protein has the ability to combine with the
antigen that stimulated its production.antigen that stimulated its production.

Antigen (Ag): Antigen (Ag): A substance that can react with A substance that can react with
an antibody. Not all antigens can induce an antibody. Not all antigens can induce
antibody production; those that can are also antibody production; those that can are also
called immunology.called immunology.

43. 
B cell (also B lymphocyte): B cell (also B lymphocyte): Strictly, a bursa–Strictly, a bursa–
derived cell in avian species and, by analogy, a derived cell in avian species and, by analogy, a
cell derived from the equivalent of the bursa in cell derived from the equivalent of the bursa in
non-avian species. B cells are the precursors of non-avian species. B cells are the precursors of
plasma cells that produce antibody.plasma cells that produce antibody.

Cell – mediated (cellular) immunity: Cell – mediated (cellular) immunity:
Immunity in which the participation of Immunity in which the participation of
lymphocytes and macrophages is predominant. lymphocytes and macrophages is predominant.
Cell–mediated immunity is a term generally Cell–mediated immunity is a term generally
applied to the type IV hypersensitivity reaction.applied to the type IV hypersensitivity reaction.

44. 
Chemokines: Chemokines: low–molecular–weight protein that low–molecular–weight protein that
stimulate leukocyte movement.stimulate leukocyte movement.

Chemotaxis: Chemotaxis: A process whereby phagocytic cells A process whereby phagocytic cells
are attracted to the vicinity of invading pathogens.are attracted to the vicinity of invading pathogens.

Complement: Complement: A set of plasma proteins that is the A set of plasma proteins that is the
primary mediator of antigen-antibody reactions.primary mediator of antigen-antibody reactions.

Cytolysis: Cytolysis: The lysis of bacteria or of cells such as The lysis of bacteria or of cells such as
tumor or red blood cells by insertion of the tumor or red blood cells by insertion of the
membrane attack complex derived from membrane attack complex derived from
complement activation.complement activation.

45. 
Cytotoxic T cell: Cytotoxic T cell: T cells that can kill other T cells that can kill other
cells infected with intracellular pathogens.cells infected with intracellular pathogens.

Endotoxins: Endotoxins: Bacterial toxins released from Bacterial toxins released from
damaged cells.damaged cells.

Epitope: Epitope: Site on an antigen recognized by an Site on an antigen recognized by an
antibody. Also known as an antigenic antibody. Also known as an antigenic
determinantdeterminant

Hapten: Hapten: A molecule that is not immunogenic A molecule that is not immunogenic
by itself but can react with specific antibody.by itself but can react with specific antibody.

46. 
Histocompatible: Histocompatible: Sharing transplantation Sharing transplantation
antigens.antigens.

Humoral immunity: Humoral immunity: Pertaining to immunity Pertaining to immunity
in a body fluid and used to denote immunity in a body fluid and used to denote immunity
mediated by antibody and complement.mediated by antibody and complement.

Immune response: Immune response: Development of Development of
resistance (immunity) to a foreign substance resistance (immunity) to a foreign substance
(e.g., infectious agent). It can be antibody-(e.g., infectious agent). It can be antibody-
mediated (humoral) ,cell-mediated (cellular), mediated (humoral) ,cell-mediated (cellular),
or both.or both.

47. 
Innate immunity: Innate immunity: Nonspecific resistance not acquired Nonspecific resistance not acquired
through contact with an antigen. It includes skin and through contact with an antigen. It includes skin and
mucous membrane barriers to infectious agent and a mucous membrane barriers to infectious agent and a
variety of non specific immunologic factors, and it may variety of non specific immunologic factors, and it may
vary with age and hormonal or metabolic activity.vary with age and hormonal or metabolic activity.

  Adjuvants:Adjuvants: Substances that enhance the immune Substances that enhance the immune
response to an antigen when administered alongresponse to an antigen when administered along with with
that particular antigenthat particular antigen

Adaptive immunity: Adaptive immunity: Protection acquired by deliberate Protection acquired by deliberate
introduction of an antigen into a responsive host. introduction of an antigen into a responsive host.
Active immunity is specific and is mediated by either Active immunity is specific and is mediated by either
antibody or lymphoid cells (or both)antibody or lymphoid cells (or both)

48. 
Immunoglobulin: Immunoglobulin: A glycoprotein, composed of H and L A glycoprotein, composed of H and L
chain, that functions as antibody. All antibodies are chain, that functions as antibody. All antibodies are
immunoglobulin, but not all immunoglobulin have immunoglobulin, but not all immunoglobulin have
antibody function.antibody function.

Inflammation: Inflammation: Local accumulation of fluid and cells Local accumulation of fluid and cells
after injury or infection.after injury or infection.

Interferon: Interferon: One of a heterogeneous group of low-One of a heterogeneous group of low-
molecular-weight proteins elaborated by infected host molecular-weight proteins elaborated by infected host
cells that protect noninfected cells from viral infection. cells that protect noninfected cells from viral infection.
Interferons, which are cytokines, also have Interferons, which are cytokines, also have
immunomodulating functions.immunomodulating functions.

Leukocyte: Leukocyte: General term for a white cell.General term for a white cell.

Lymphocyte: Lymphocyte: A molecule cell 7-12pm in diameter A molecule cell 7-12pm in diameter
containing a nucleus with densely packed chromatin containing a nucleus with densely packed chromatin
and a small rim of cytoplasma, lymphocytes include the and a small rim of cytoplasma, lymphocytes include the
T cells and B cells, which have primary roles in T cells and B cells, which have primary roles in
immunity.immunity.

49. 
Macrophage: Macrophage: A phagocytic mononuclear cell derived A phagocytic mononuclear cell derived
from bone marrow monocyte and found in tissues from bone marrow monocyte and found in tissues
and at the site of inflammation. Macrophages serve and at the site of inflammation. Macrophages serve
accessory roles in immunity, particularly as antigen accessory roles in immunity, particularly as antigen
presenting cells(APCs).presenting cells(APCs).

Major histocompatibility complex(MHC): Major histocompatibility complex(MHC): A cluster A cluster
of genes located in close proximity eg, on human of genes located in close proximity eg, on human
chromosomes 6, that encoded the histocompability chromosomes 6, that encoded the histocompability
antigens (MHC molecules)antigens (MHC molecules)

Membrane attack complex: Membrane attack complex: The end product of The end product of
activation of the complement cascade, which contains activation of the complement cascade, which contains
C5, C6, C7, and C8 (and C9). The membrane attack C5, C6, C7, and C8 (and C9). The membrane attack
complex makes holes in the membrane of gram-complex makes holes in the membrane of gram-
negative bacteria killing them and, in red blood or negative bacteria killing them and, in red blood or
other cells, resulting in lysis.other cells, resulting in lysis.

50. 
Monoclonal antibodies: Monoclonal antibodies: Each B lymphocyte Each B lymphocyte
produces antibody of a single specificity on produces antibody of a single specificity on
hybridization. hybridization.

Monocyte: Monocyte: A circulating phagocytic blood cell A circulating phagocytic blood cell
that develops into tissue macrophages.that develops into tissue macrophages.

Natural killer (NK) cells: Natural killer (NK) cells: Large lymphoid Large lymphoid
cells with no known antigen-specific cells with no known antigen-specific
receptors. They are able to recognize and kill receptors. They are able to recognize and kill
certain abnormal cells, e g tumor cells.certain abnormal cells, e g tumor cells.

51. 
Opsonin: Opsonin: A substance capable of enhancing A substance capable of enhancing
phagocytosis. Antibodies and complement phagocytosis. Antibodies and complement
are the two main opsoninsare the two main opsonins

Opsonization: Opsonization: The coatings of an antigen or The coatings of an antigen or
particle (e.g., infectious agent) by substances, particle (e.g., infectious agent) by substances,
such as antibodies, complement such as antibodies, complement
components, fibronectin, and so forth, that components, fibronectin, and so forth, that
facilitate uptake of the foreign particle into a facilitate uptake of the foreign particle into a
phagocytic cell.phagocytic cell.

52. ENDEND