AGB 453 DEFENSE MECHANISMS IN ANIMALS.pdf

This document is a presentation by my professor on defense mechanism in animals

1. AGB 452 DEFENSE
MECHANISMS IN ANIMAL
*DR. FRANK IDAN
PROF. A. DONKOH

2. ACADEMIC BACKGROUND
Senior High School –Aggrey Memorial Zion SHS, Cape Coast
BSc. (Hons) Agriculture–University of Cape Coast, Cape Coast
MPhil Animal Science (Ruminant Nutrition) –University of Ghana,
Legon, Accra
PhD Grain Science –Kansas State University, Manhattan, Kansas, US
Teaching Philosophy
❑Every student has the potential to excel when given the right
opportunities and guidance
❑Students need to stay focus, work hard, and be committed to their
academic work to succeed

3. BODY DEFENSE MECHANISMSAGAINST
PATHOGENS
All living organisms are continuously exposed to
substances that are capable of causing them harm
The body has developed defense mechanisms to control
and to cope with the constant attack of microorganisms

4. BODY DEFENSE MECHANISMSAGAINST
PATHOGENS
Animals have both specificand non-specificdefense
mechanisms to fight invaders.
Specific defense mechanisms are effective against
specific pathogens and involves various white blood cells
called lymphocytes or leukocytes

5. BODY DEFENSE MECHANISMSAGAINST
PATHOGENS
Non-specific defense mechanismswork against a wide variety of
invaders and include:
❑Barrier formed by the skin
❑Chemicals in perspiration, skin oil, saliva, tears
❑Hairs in the nostrils
❑Ciliary escalator (the cilia and mucus that clean out dust and debris
from the lungs and trachea) in the respiratory tracts
❑Inflammatory response which is the dilation of blood vessels and
accumulation of white blood cells at the site of an injury
❑Fever, a raised body temperature to inhibit the growth of pathogens

6. BODY DEFENSE MECHANISMS
Thebodyhasthreelinesofdefense:
❑PhysicalBarriers
❑DefensiveCells&Proteins,Inflammation,andFever
❑TheImmuneSystem

7. SUMMARY OF DEFENSE MECHANISMS OF
THE HUMAN BODY

9. THE FIRST LINE OF DEFENSE
Theseareacombinationofphysicaland
chemicalbarriersthatpreventalltypesofforeign
agentsfrompenetratingtheouterlayerofthe
body
Nospecificforeignagentistargetedatthislevel

10. PHYSICAL BARRIERS
1.SKIN
Cellsfilledwithkeratin,makingskinimpenetrable,
waterproof,andresistanttodisruptivetoxinsand
mostinvaders
Deadcellsareshedandreplaced(1millionevery
40min),takingmicrobeswiththem

12. PHYSICAL BARRIERS
2.MUCOUSMEMBRANES:
Theinnersurfacesofthebodyareguardedbymucous
membranesthatlinetherespiratory,digestive,urinary,and
reproductivesystemsandprotecttheinternallining
Themucuslayertrapspathogens(potentiallyinfectious
microorganisms)andotherparticles,preventingthemfrom
reachingthelungs
But,mucousmembranesaremorevulnerablethanskin

15. PHYSICAL BARRIERS
3. HAIR IN THE NOSE:
Most vertebrates active respire continuously
Inevitably, this air contains potentially harmful particles
and gases
The hair in the nose act as a coarse filter (defense
mechanism)against particles such as dust and soot

16. CHEMICAL BARRIERS
1.SWEAT:
Producedbyglandsintheskinwashaway
microbesand theiracidityslowsbacterial
growth.

17. CHEMICAL BARRIERS
2. MUCOUS MEMBRANES:
Produce sticky mucus that traps many microbes

19. CHEMICAL BARRIERS
3. SALIVA AND TEARS:
Contain an enzyme called lysozyme that kills
bacteria by rupturing their cell walls

21. CHEMICAL BARRIERS
4. CERUMEN (EAR WAX):
Produced in the outer part of the ear canal and protects
the canal by trapping dirt and dust particles
Composed of dead skin cells and hair combined with
discharge
The wax has both lubricating and antibacterial properties

22. CHEMICAL BARRIERS
5. LACTATE (Lactic acid):
•Primary acid present in the
vaginal lumen of women and the
principal determinant of acidic
vaginal pH
•Originates from 2 sources: resident
bacteria(lactobacillus) and
vaginal epithelial cells

23. CHEMICAL BARRIERS
6. HCl in Stomach:
•Primary aim is to break down, digest, and absorb nutrients esp.
protein
•Eliminates bacteria and viruses in the body thus protecting it
against infection
7. Spermine:
•Component of the non-sperm part of the ejaculated semen that
facilitates delivery of sperm to the egg
•It is antimicrobial hence inhibits bacteria in the male urogenital
tract

24. THE SECOND LINE OF DEFENSE
1.DEFENSIVECELLS
Ifapathogenpenetratesthefirstlineofdefense,these
cellsplayaroleininhibitingordestroyingthepathogen
beforeitharmsthebody
They are non-specific and react to the presence of any
foreign organism or substance

25. 1. DEFENSIVE CELLS
(a)Phagocytes:
Engulfpathogens,foreignmaterials,damagedtissue,ordeadcells
Canalsoboostimmunesystem
Consistoftheff:
▪Neutrophils:atypeofwhitebloodcellsinvolvedintheimmuneresponse.
Theydetectinvaders,eatthemandkillthem
▪Macrophages:type of white blood cells that clean the body of
unwanted microscopic particles, such as bacteria and dead cells
▪Monocytes:made in the bone marrow and travels through the
blood to tissues to become dendritic cells. Boost immune response
by showing antigens on their surfaces

26. 1. DEFENSIVE CELLS
(b) Eosinophils
Specialized white blood cells that help to fight parasitic infections
Discharge destructive enzymes to destroy pathogens too big for
phagocytes (e.g., parasitic worms)
Release of eosinophils indicates a parasitic infection, an allergic
reaction or cancer
High levels of eosinophils in the blood (blood eosinophilia) or in tissues at the site of
an infection or inflammation (tissue eosinophilia)

27. 1. DEFENSIVE CELLS
(c) Natural Killer (NK) Cells
A type of immune cell that has granules (small particles) with
enzymes that can kill tumor cells or cells infected with a virus
Or
Innate immune cells that show strong cytolyticfunction
against physiologically stressed cells such as tumor cells and
virus-infected cells
Seek out abnormal cells (e.g., cancer cells)

28. 2. DEFENSIVE PROTEINS
Alsocalledantibodiesorimmunoglobulinsarethe
centralmostimportantpartoftheentireimmune
system
Havebindingsiteswhosethree-dimensionalstructure
allowsthemtoidentifyandbindtoveryspecificforeign
molecules

29. 2. DEFENSIVE PROTEINS
(a) Interferon
A group of signaling proteins made and released by host cells in
response to the presence of several pathogens, such as viruses,
bacteria, parasites, and also tumor cells.
A virus enters a cell, then the infected cell produces interferon
In a typical scenario, a virus-infected cell will release interferons
causing nearby cells to heighten their anti-viral defenses.

30. 2. DEFENSIVE PROTEINS
(a) Interferon
Binds with other cells that become infected with a virus,
and protects it by stimulating the cell to produce antiviral
proteins that prevent the virus from making copies of
itself
Attracts and stimulates natural killer (NK) cells and
macrophages to kill cells infected with the virus

31. 2. DEFENSIVE PROTEINS
(b) Complement System (CS)
Made up of a large number of distinct plasma proteins that react
with one another to enable antibodies and phagocytic cells to
clear pathogens and induce a series of inflammatory responses
that help to fight infection
Functions
❑Destruction of pathogen (Cell lysis)
❑Enhancement of phagocytosis
❑Stimulation of inflammation
❑Chemotaxis -attracting macrophages & neutrophils

32. 3. INFLAMMATION
Nonspecific response to any trauma occurring to tissues as a
result of injury or damage
Damaged tissues cause a series of events called the
inflammatory response occurs
Signs and symptoms of Inflammation
❑Redness:caused by increased blood flow to the damaged
area

33. 3. INFLAMMATION
❑Heat: Increased blood flow elevates the temperature
in the area of injury, increasing metabolic rate of the
body cells
❑Swelling: histamine makes capillaries more
permeable than usual.
❑Pain: causes individual to protect the area and
prevent additional injury.

34. 4. FEVER
A fever is an abnormally high body temperature caused
by pyrogens (chemicals that set the “thermostat” in the
brain to a higher set point)
A mild or moderate fever helps the body fight bacterial
infections by slowing the growth of bacteria and
stimulating body defense responses

35. THE THIRD LINE OF DEFENSE
(a) The Immune System: complex network of organs containing
cells that recognize foreign substances in the body and destroy them
Immunity means protection from infections
The cells and molecules responsible for immunity constitute
the immune system
Their collective and coordinated response to the foreign
substance, i.e. Infectious agents is called the immune
response

36. (a) The Immune System
When the first 2 lines of defense of the body cannot prevent
the infection, the immune system acts to eliminate the
infectious agent and prevent the body from infection
Immune response/ immunity generally consists of two steps:
❑Step-1:Recognition of the pathogen or foreign molecule
❑Step-2:Mounting reaction against the pathogen

38. 1. Natural Immunity
Immunity/antibody protection acquired from exposure to the
disease organism through infection with the actual disease
It is resistance to a disease possessed by an individual.
Nature has given certain individuals, species and races immunity
against certain disease.
E.g., some individuals are more resistant to certain infections than
others

39. 2. Acquired Immunity
With only the natural immunity, it is not possible to fight off each
and every infection and survive.
So, immunity is induced in individuals by certain ways.
Acquired immunity is developed during a person’s lifetime; it is not
inherited and can be acquired actively or passively
This occurs when the immune system responds to a foreign
substance or microbe or after a person receives antibodies from
another source

40. 2.1. Naturally Acquired Active Immunity
This immunity is acquired when a person or animal is
exposed to natural infections or to some antigens in the
day-to-day life.
Following the exposure, the immune system responds by
producing antibodies

41. 2.2 Artificially Acquired Active Immunity:
This immunity is acquired by administering specially
prepared antigens which produce specific antibodies.
This is also known as vaccinationwhere inactivated
bacterial toxins (toxoids), killed or living but attenuated
micro-organisms are administered to the body wherein
they lose their ability to cause disease but still capable of
stimulating the immune system

42. 2.3 Naturally Acquired Passive Immunity:
This involves natural transfer of antibodies from a mother
to a fetus via placenta or breast milk and thus providing
immunity to the new born for a few days to a few
months.
Here, the fetus is immune to those diseases for which the
mother is immune, but for a short period of time.

43. 2.4 Artificially Acquired Passive Immunity
Here antibodies are directly administered to body for
stimulation of immune response.
These antibodies are either produced in animals or in
humans and they are found in the serum after
administration

44. OTHER CLASSIFICATION OF IMMUNITY
Again, immunity can be broadly classified into two categories:
(A) Adaptive immunity
(B) Innate immunity
(A)Adaptive immunity: occurs in response to being infected
with or vaccinated against a microorganism
Can be further divided into two types:
❑Humoral immunity
❑Cell mediated immunity

45. OTHER CLASSIFICATION OF IMMUNITY
A. Innate Immunity
❑Innate Immunity reflects the first and second line of defense
against infections
❑It usually exists before encountering an infectious agent i.e. it
is the defense mechanism which is present as inherent.
❑Its mechanism is non-specifici.e. they are not dependent on
specific recognition of a foreign material rather a mechanism
which can provide protection against different pathogens

46. Components of Innate Immunity
Physical and chemical barriers
❑Skin
❑GIT and acidic environment of
stomach
❑Respiratory tract
❑Tears, saliva, sweat
❑Effector cells
❖Phagocytes, for example,
macrophages, neutrophils
❖Natural killer (NK) cells
❑Blood protein
❖Complement system
❖Antibody
❑Cytokines

47. Physical and chemical barriers
Cytokinesare molecules used for communication
between cells to trigger the protective defenses of the
immune system that help eradicate pathogens.

48. Adaptive Immunity
Consists of defense mechanism which are stimulated by
exposure to infectious agents
Its mechanism is specific because of its ability to
distinguish among different, even closely -related
infectious agents

49. Adaptive Immunity
Adaptive Immunity is of 2 types: Humoraland Cell:
Humoral Immunity:
❑It is mediated by antibodies, produced by B lymphocytes
(matured in the bone marrow).
❑It is the principal defense mechanism against
extracellular microbes and their toxins and assist in their
elimination

50. Adaptive Immunity
Cell Mediated Immunity
❑Cell mediated immunity is mediated by cytokines,
produced by T lymphocytes (matured in Thymus
Glands)
❑It is the defense mechanism against intracellular
microbes

51. Cell Mediated Immunity
Two types of T cell regulate the cell mediated
immunity such as:
❑Helper T Cells (TH)
❑Cytotoxic/Cytolytic T Cells (CTL)

53. Helper T cells
Most important cells in adaptive immunity.
They are required for almost all adaptive immune
responses.
They not only help activate B cells to secrete antibodies
and macrophages to destroy ingested microbes, but
they also help activate cytotoxic T cells to kill infected
target cells.

54. Helper T cells
As dramatically demonstrated in AIDS patients, without
helper T cells, they cannot defend themselves even
against many microbes that are normally harmless.
Helper T cells themselves can only function when
activated to become effector cells.

55. Helper T cells
They are activated on the surface of antigen-presenting
cells, which mature during the innate immune responses
triggered by an infection.
The innate responses also dictate what kind of effector
cell a helper T cell will develop into & thereby determine
the nature of the adaptive immune response elicited.

56. Cytotoxic/ Cytolytic T Cells (CTL)
AlsoknownasT
C,cytotoxicTlymphocyte,CTL,T-killer
cell,cytolyticTcell,CD8+T-cellorkillerTcell)
ItisaTlymphocyte(atypeofwhitebloodcell)thatkills
cancercells,cellsthatareinfected(particularlywith
viruses),orcellsthataredamagedinotherways.

57. Cytotoxic/ Cytolytic T Cells (CTL)
MostcytotoxicTcellsexpressT-cellreceptors(TCRs)that
canrecognizeaspecificantigen.
Anantigenisamoleculecapableofstimulatingan
immuneresponse,&isoftenproducedbycancercells
orviruses.

58. Cytotoxic/ Cytolytic T Cells (CTL)
AntigensinsideacellareboundtoclassIMHC
molecules,&broughttothesurfaceofthecellbythe
classIMHCmolecule,wheretheycanberecognizedby
theTcell.
IftheTCRisspecificforthatantigen,itbindstothe
complexoftheclassIMHCmoleculeandtheantigen,
andtheTcelldestroysthecell.

59. Cytotoxic/ Cytolytic T Cells (CTL)
InorderfortheTCRtobindtotheclassIMHCmolecule,
theformermustbeaccompanied byaglycoprotein
calledCD8,whichbindstotheconstantportionofthe
classIMHCmolecule.
Therefore,theseTcellsarecalledCD8+Tcells.

60. Cytotoxic/ Cytolytic T Cells (CTL)
TheaffinitybetweenCD8andtheMHCmoleculekeeps
theTCcellandthetargetcellboundcloselytogether
duringantigen-specificactivation.
CD8+TcellsarerecognizedasTCcellsoncethey
becomeactivated&aregenerallyclassifiedashavinga
pre-definedcytotoxicrolewithintheimmunesystem.
However,CD8+Tcellsalsohavetheabilitytomakesome
cytokines.