Introduction to Immunology

Immune system

1. Introduction to Immunology
Lecture 1
2
nd
stage
Hawler Medical University
College of Health Sciences
Medical Microbiology Dept.
Dr. Amer Ali Khaleel
(Medical Immunology)
[email protected]

2. Concept of Immunity:
•ThewordImmunology,whichcomesfromtheLatin=immunis=“exempt;”
English=protectionfromdisease(resistance).
•So,Immunologyisthestudyofthewayinwhichbodydefendsitselffrom
infectiousagents.
•Immunity:Theabilityofanorganismtorecognizeanddefenditselfagainst
specificpathogensorantigens.Thecellsandmoleculesresponsibleforimmunity
constitutetheimmunesystem,andtheircollectiveandcoordinatedresponseto
foreignsubstancesiscalledtheimmuneresponse.

3. What is the Immune System?
•TheImmunesystemisabiologicalstructureandprocesseswithinan
organismthatprotectsagainstdiseasebyidentifyingandkilling
pathogensandtumorcells.
•Itdetectsawidevarietyofagents,fromvirusestoparasiticworms,
andneedstodistinguishthemfromtheorganism'sownhealthycells
andtissuesinordertofunctionproperly.

4. Structureof the Immune System:
•Theimmunesystemhasamultilayeredarchitecturewith
defensesprovidedatmanylevels.
•Theimmunesystemisacomplexnetworksecuritysystemof
chemicals,cells,tissuesandorgansthatworktogethertoprotect
thebody.

5. The Functions of the Immune System:
•Withoutanimmunesystem,ahumanbeingwouldbejustas
exposedtotheharmfulinfluencesofpathogensorother
substancesfromtheoutsideenvironmenttoinsideofthe
body.

6. The main tasks of the body’s immune system are:
1. Classifyingability to distinguish between the body’s own cells (self) and foreign
cells (non-self).
2. It provides defenses against pathogens likebacteria,viruses,parasitesor fungi.
3. Identifying-ability to distinguish one pathogen from another.
4.Itremoves (Scavenges) dead or worn out cells like RBCs.
5.It identifies and destroys abnormal cancer cells.
6.It protects against autoimmune diseases.
7.It rejects tissue cells with foreign antigens.
8. Remembering: The ability to remember previously encountered pathogens.
9. Switch on: The ability to respond when a pathogen invades.
10.Switch off: The abilityto stop when danger passes.

7. Differentiation between self and non self substances:
•Forprotectiontobeeffectiveitisimportant,however,thatthe
immunesystemcandifferentiatebetween“selfantigen”and“non-
self(foreign)”antigencell,organismsandallthebiological,
chemical,physiological,metabolic,andphysicalaspectsofthe
immuneresponse.
•Usually,thebodyshouldnotworkagainstitsownhealthycells.

8. Differentiation between self and non self substances:
•Allcells,aswellassomeparticlessuchaspollen,displayaunique
mixofmacromoleculesontheirsurfacesthattheimmunesystem
“senses”todetermineiftheyareforeignornot.Thesechemicalsare
calledantigens.Becauseforeigncellsorparticlescouldpotentially
enterthroughanynumberofportals,thecellsoftheimmunesystem
constantlymoveaboutthebody,searchingforpotentialpathogens.
Thisprocessiscarriedoutprimarilybywhitebloodcells,whichhave
beentrainedtorecognizebodycells(so-calledself)anddifferentiate
themfromanyforeignmaterialinthebody,suchasinvading
microorganismcells(non-self).

9. Figure: Search, recognize, and destroy is the mandate of the immune system.
White blood cells are equipped with a very sensitive sense of “touch.” As they
travel through the tissues, they feel surface markers that help them determine
what is self and what is not. When self markers are recognized, no response
occurs. However, when non-self is detected, a reaction to destroy it is mounted.

11. Differentiation between self and non self substances:
•Theimmunesystemisdesignedtodefendthebodyagainstforeignor
dangerousinvadersincluding:-
1.Microorganisms (commonly called germs) such as bacteria, viruses,
fungi (yeastsandmolds) & parasites (such as worms).
2.Innocuous (not harmful or offensive) substances (such as allergy).
3.Transplanted organs and tissues.
4.Cancer cells.

12. Differentiation between self and non self substances:
•Manyautoimmunedisordersarearesultoftheimmunesystem
mistakenlyattackingthebody’sowntissuesandorgans.Forexample,
inrheumatoidarthritis,thebodyattacksitsownjointsandtissues,
causingpainandlossoffunction.

13. •Theimmunesystemcanbeactivatedbymany“non-self”
substances.Thesearecalledantigens(Ag).Theproteinsonthe
surfacesofbacteria,fungiandviruses,forexample,areall
antigens.
•Whentheantigensbindto,forexample,specialreceptorson
thedefensecells,aseriesofcellprocessesisstarted.Thenthe
immunesystemcanrecallstored“memories”inordertomore
quicklybereadytodefendagainstknownpathogens.
Differentiation between self and non self substances:

14. The state of unresponsiveness of the immune system
to antigen.
Or
A state of unresponsiveness to a specific antigen or
group of antigens to which a person is normally
responsive.
Immune Tolerance:

15. The state of unresponsiveness of the immune system to self-
antigen.
Or
The physiological state that exists in an organism when its
immune system has proceeded far enough in the process of
self-recognition to lose the capacity to attack and destroy its
own bodily constituents.
Self-Tolerance:

16. + There is immune response
-There is no immune response
LEAD TO
* Apoptotic cells is a form ofprogrammed cell death.
*Homeostasis Maintaining a stable internal condition is
crucial to any form ofliving thing.

17. (irregular)

18. Terminology:
CDnomenclature:
•CDstandsforclusterofdifferentiation.Thisisaclassification
systemforthedifferentantigenicdeterminantsfoundoncells.The
surfacemoleculesofdifferenttypesofcellsandsoactasmarkersof
differentiation.ThedifferentCDcomplexesaregivenanumberto
differentiatethem.
•Wellover300CDmoleculeshavebeennamed.
•ManyCDmolecules,orCDsforshort,areinvolvedintheimmune
response.

20. The Role of Markers and Receptors in Presentation and
Activation:
•Allcellsbothforeigncellsand“self”cellshaveavarietyofdifferent
markersontheirsurfaces,eachtypeplayingadistinctandsignificant
roleindetection,recognition,andcellcommunication.
•Cellmarkersplayimportantrolesintheimmuneresponse,servingto
activatedifferentcomponentsofimmunity.Becauseoftheir
importanceintheimmuneresponse.

21. Any Questions
??!!!
Next lecture
Cells Of The Immune System