1. The document summarizes the defense mechanisms of the human body against infection. It discusses both innate immunity, which provides immediate nonspecific defenses like skin barriers and phagocytosis, and adaptive immunity, which involves acquired immunity through humoral or cell-mediated responses with immunological memory. 2. The four types of acquired immunity are described as natural active, natural passive, artificial active through vaccination, and artificial passive through antibodies. The differences between humoral immunity mediated by antibodies and cell-mediated immunity triggered by T-cells are also outlined. 3. Key innate defenses include physical barriers from skin and mucous membranes, phagocytosis by cells, and soluble proteins. Adaptive immunity has specificity and memory and involves B cells

1. Defense Mechanisms of the
Human Body
PresentedByRaheelRoyl,Usamasami,
MaryalJane,AbdulRazzak,Shamshad.
[GroupC]
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Presented toMr.ImtiazAliAbbasi

2. Objectives:
1.Explaintheroleofgoodhealthinprotectionagainstthemicrobialinfection.
2.Defineresistanceandsusceptibility.
3.Defineimmunity.
4.Definetheinnateresistance.
5.Describetheroleoftheskinandmucousmembraneinnonspecificresistance.
6.Explaintheprocessofphagocytosis.
7.DefineAdaptiveimmunity(specificresistance).
8.Explainfourtypesofacquiredimmunity.
9.Differentiatebetweenhumoralandcellmediatedimmunity.
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3. 10.Defineantigensandantibodies.
11.Listthefiveclassesofantibodiesandtheirfunctions.
12.Explaintheroleofmemory,toleranceandspecificityinimmunity.
13.Distinguishbetweenprimaryandsecondaryimmuneresponse.
14.DefineHypersensitivity.
15.DifferentiatebetweendelayedandimmediateHypersensitivity.
16.Roleplay(dressingofwounds)
Ultimately,theaimofadressingistopromotehealingofthewoundbyprovidingasterile,breathable
andmoistenvironmentthatfacilitatesgranulationandepithelialization.Thiswillthenreducetheriskof
infection,helpthewoundhealmorequickly,andreducescarring.
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4. Alllivingthingsaresubjecttoattackfromdisease-causingagents. Evenbacteria,sosmallthat
morethanamillioncouldfitontheheadofapin,havesystemstodefendagainstinfection by
viruses.Thiskindofprotection getsmoresophisticated asorganismsbecomemorecomplex.
Multicellularanimalshavededicatedcellsortissuestodealwiththethreatofinfection.Someof
theseresponses happenimmediatelysothataninfecting agentcanbequicklycontained.Other
responses areslowerbutaremoretailoredtotheinfecting agent.Collectively,theseprotections
areknownastheimmunesystem.Thehumanimmunesystemisessentialforoursurvivalina
worldfullofpotentiallydangerousmicrobes, andseriousimpairmentofevenonearmofthis
systemcanpredispose tosevere, evenlife-threatening, infections.
1. ROLE OF GOOD HEALTH IN PROTECTION AGAINST THE
MICROBIAL INFECTION:
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5. Resistanceisdefinedastheabilitytolimitpathogenorthequalityorstateof
beingimmune.
Especially:aconditionofbeingabletoresistaparticulardiseaseespecially
throughpreventingdevelopmentofapathogenicmicroorganismorby
counteractingtheeffectsofitsproducts.
2. DEFINITION OF RESISTANCE:
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⦁ SUSCEPTIBLE:
Susceptibleislikelyorliabletobeinfluencedorharmedbyapathogenand
susceptibilityisaconditioninwhichtheindividualisatariskofgetting
infectedbyadisease.

6. 3. Immunity:
Immunityisthecapabilityofmulticellularorganismstoresistharmful
microorganisms,aconditionofbeingabletoresistaparticulardisease
especiallythroughpreventingdevelopmentofapathogenic
microorganismorbycounteractingtheeffectsofitsproducts.Thetasksof
theimmunesystemaretofightdisease-causinggerms(pathogens)like
bacteria,viruses,parasitesorfungi,andtoremovethemfromthebody.
Humanshavethreetypesofimmunity—innate,adaptive,andpassive:
.
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7. Nonspecificresistanceisthedefenseofourbodyfromanykindsofthe
pathogens.Itsskinandmucousmembrane,phagocytosis,
inflammation,fever,productionofantimicrobialsubstances.
Innatedefensesareclassifiedintothreemajorcategories:
(1)Physicalbarriers,suchasintactskinandmucous.
(2)Phagocyticcells,suchasneutrophilsandmacrophages.
(3)Protein,suchascomplementandlysozyme.
4. NON-SPECIFIC (INNATE) RESISTANCE:
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Itincludesbothfirstandsecondlineofdefense.

8. 5A. ROLE OF SKIN MEMBRANE IN NON-SPECIFIC RESISTANCE:
Thebody’smostimportantnon-specificdefenseistheskin.Itisthefirstlineof
defenseagainstmanyorganisms,whichactsasaphysicalbarriertokeep
pathogensout.Evenopeningsintheskin(suchasthemouthandeyes)are
protectedbysaliva,mucus,andtears.Inadditiontothephysicalbarrier
presentedbyskin,thefattyacidssecretedbysebaceousglandsintheskin
haveanantibacterialandantifungalactivity.
First Line of Defense
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9. 5B. ROLE OF MUCOUS MEMBRANE IN
NON-SPECIFIC RESISTANCE:
Asecondimportantdefenseisthe
mucousmembrane.Themucous
membranesliningthenose,mouth,
lungs,urinary,anddigestivetracts
provideanothernonspecificbarrier
againstpotentialpathogens.
Example,themucousmembraneof
therespiratorytract.
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10. 6. DEFINE PHAGOCYTOSIS:
Phagocytosisistheprocessbywhichacellusesitsplasmamembranetoengulfor
ingestalargeparticle,givingrisetoaninternalcompartmentcalledPhagosome.A
cellthatperformsphagocytosisiscalledphagocyte.Thephagocytemaybefree-
livingone-celledorganism,suchasanamoeba,oroneofthebodycells,suchas
whitebloodcells.
Followingarethefivestagesofphagocytosis:
1.Chemotaxis:Movementinresponsetochemicalstimulation.Pseudopodsmove
towardmicroorganismatsiteofinfection.
2.Adherence:Attachmenttoamicrobe.
3.Ingestion:engulfingpathogenwithpseudopodiawrappingaroundpathogen.
4.Digestion:Phagosomematuration,microbesareactuallykilledatthispoint.
5.Elimination:Phagocyteseliminateremainingpiecesofmicrobeviaexocytosis.
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11. Theadaptive,oracquired,immuneresponsetakesdaysorevenweeksto
becomeestablished—muchlongerthantheinnateresponse;however,
adaptiveimmunityismorespecifictopathogensandhasmemory.Adaptive
immunityisanimmunitythatoccursafterexposuretoanantigeneitherfroma
pathogenoravaccination.
7. Adaptive immunity:
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Adaptiveimmunityalsoinvolvesa
memorytoprovidethehostwithlong-
termprotectionfromreinfectionwiththe
sametypeofpathogen;onre-exposure,
thismemorywillfacilitateanefficientand
quickresponse.
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Defense

12. 1) Natural Actively Acquired Immunity:
Naturallyacquiredactiveimmunityoccurswhenthepersonisexposedtoalive
pathogen,developsthedisease,andbecomesimmuneasaresultoftheprimary
immuneresponse.TheInfectioncauseproductionofantibodiesagainst
pathogens.Itislonglasting.Theantigensonthesurfaceofthepathogens
causesimmuneresponse.
Forexample:Chickenpox,hepatitisAvirus,etc.
8. FOUR TYPES OF ACQUIRED IMMUNITY:
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13. 2) Natural Passively Acquired Immunity:
Naturallyacquiredpassiveimmunityoccursduring
pregnancy,whenantibodiesarepassedfromthematernal
bloodintothefetalbloodstream,andviabloodstream.Itis
usuallyforshortperiodoftime.
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3) Artificial Actively Acquired Immunity:
Apersoncanbuildaresistancetoadiseasefollowinganimmunization.Vaccinesuse
aweakenedordeadformofadisease(bacteriaorvirus)tostimulateanimmune
response.Whenaperson’simmunesystemdetectstheweakenedordead
pathogen,itbeginstotakestepstodestroyit.Thisincludesformingnewantibodies
andmemorycellsspecifictothatpathogen,itlastsLonger.

14. 4) Artificial Passively Acquired Immunity:
Artificially-acquiredpassiveimmunityisanimmediate,but
short-termimmunizationprovidedbytheinjectionof
antibodies/antiserum/antitoxins.
Theseantibodiesmaycomefromthepooledandpurified
bloodproductsofimmunepeopleorfromnon-human
immuneanimals.Therabiesvaccineandsnakeantivenom
aretwoexamplesofantiserumsthatyieldpassiveimmunity.
Forexample:Tetanusvaccine.
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15. Humoralimmunityandcellmediatedimmunityaretwotypesofadaptive
immunity.Adaptiveimmunitygeneratesanantigen-specificimmune
response.Themaindifferenceiscellmediateddoesnotproduce
antigen-specficantibody,whereasinhumoralantibodiesareproduced.
9. HUMORAL AND CELL MEDIATED IMMUNITY:
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 HumoralimmunityistriggeredbyBcells,
 WhilecellmediatedimmunityistriggeredbyTcells.
 Tcellsdestroytheinfectedcellsbyinducingapoptosis.
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16. ⦁ Cell Mediated Immunity:
Cell-mediatedimmunityisanimmuneresponsethatdoesnotinvolve
antibodies.Rather,cell-mediatedimmunityistheactivationof
phagocytes,antigen-specificcytotoxicT-lymphocytes,andtherelease
ofvariouscytokinesinresponsetoanantigen.
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Activatedantigen-specificcytotoxicTcellsareabletoinduceapoptosis
(cellsuicide)inbodycellsdisplayingepitopesofforeignantigenontheir
surface,suchasvirus-infectedcells.
Itismosteffectiveinremovingvirus-infectedcells,butalso
participatesindefendingagainstfungi,protozoans,cancers,and
intracellularbacteria.Italsoplaysamajorroleintransplant
rejection.

17. Third Line of Defense
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18. ⦁ Humoral Immunity:
Thehumoralimmuneresponseismediatedbyantibodymoleculesthat
aresecretedbyBcells.Toentercells,virusesandintracellularbacteria
bindtospecificmoleculesonthetargetcellsurface.Antibodiesthatbind
tothepathogencanpreventthisandaresaidtoneutralizethepathogen.
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Humoralimmunityisnamedso
becauseitinvolvessubstancesfound
inthehumors,orbodyfluids.It
contrastswithcell-mediated
immunity.Humoralimmunityisalso
referredtoasantibody-mediated
immunity.

19. Inhumoralimmuneresponse,theBcellsfirstmatureinthebonemarrow
andgainB-cellreceptors(BCR's)whicharedisplayedinlargenumberson
thecellsurface.Thesemembrane-boundproteincomplexeshave
antibodieswhicharespecificforantigendetection.EachBcellhasa
uniqueantibodythatbindswithanantigen.ThematureBcellsthen
migratefromthebonemarrowtothelymphnodesorotherlymphatic
organs,wheretheybegintoencounterpathogens.WhenaBcell
encountersanantigen,theantigenbindstothereceptorandistaken
insidetheBcellbyendocytosis.Theantigenisprocessedandpresented
ontheBcell'ssurfaceagainbyspecificproteins.
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20. .
.
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Anantigenisamolecule,suchasmaybepresent
ontheoutsideofapathogen,thatthebody
recognizesasforeignandtriggersanimmune
responseagainstit.Anantigeninducesan
immuneresponsetoproduceantibody.
Example:virusesorbacteria.
10. Definition of Antigen:

21. ,
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⦁ Antibody:
Anantibody,alsoknownasanimmunoglobulin,isalarge,Y-shaped
proteinusedbytheimmunesystemtoidentifyandneutralizeforeign
objectssuchaspathogenicbacteriaandviruses.Theantibody
recognizesauniquemoleculeofthepathogen,calledanantigen.The
antibodiesaretransportedthroughthebloodandthelymphtothe
pathogeninvasionsite.ThebodycontainsmillionsofdifferentBcells,
eachabletorespondtoonespecificantigen.
Thereare4classesofantibodiesareIgG,IgM,IgA,IgE,IgDEach
antibodyismadeoffourpolypeptide(protein)chains:2heavychainsand
2lightchains.

22. Third Line of Defense
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23. 11.CLASSES OF ANTIBODIES/IMMUNOGLOBULINS (Ig):
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TheyarealsoknownasImmunoglobulins
Thereareonlyfivemaintypesofantibodiesfoundinthehuman
body.
Immunoglobulin-G (Ig-G)
Immunoglobulin-A (Ig-A)
Immunoglobulin-M(Ig-M)
Immunoglobulin-E(Ig-E)
Immunoglobulin-D (Ig-D)

24. 1) Immunoglobulin D (IgD):
Immunoglobulin D(IgD)accountsforonlyaround0.25%ofantibodiesinthehumanbody.IgDis
arguablytheleastunderstood antibody,withlittleknownabouthowitmightparticipateinother
partsoftheimmunesystem.
Function:Ithasavitalroleinstartingtheimmuneresponse bybindingtoBcellstoinitiatethe
immuneresponse henceactingasasignalingantibody.
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2) Immunoglobulin G (IgG):
ImmunoglobulinG(IgG)accountsforaround75%ofallantibodiesinthehumanbody.
Function:Dependingontheantigen,IgG can either tag a pathogen sootherimmunecells
andproteinswillrecognize it,oritcanpromotethereleaseoftoxinstodirectlydestroythe
microorganism.

25. 3) Immunoglobulin A (IgA):
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ImmunoglobulinA(IgA)isprimarilyfoundinmucosaltissues,suchasthoseinthemouthand
intestines, aswellasinsaliva,tears,andbreastmilk.Itaccountsfor15%ofallantibodiesinthe
humanbodyandisproducedbyBcellsandsecreted fromthelaminaproporia,athinlayer
withinmucosaltissues.
Function:IgA is one of the body's first-line defenses against infection. Itbindsto
pathogens totagthemfordestruction andpreventsthemfromstickingtotheepithelium,
whichlinesthebody'stissues.
4) Immunoglobulin M (IgM):
ImmunoglobulinM(IgM)isalsooneofthefirstantibodiesrecruited bytheimmunesystemto
fightinfection.IgMpopulationsriseveryquicklywhenthebodyisfirstconfronted withan
infectiousorganism,andthentheyplummetasIgGantibodiestakeover.
Function:IgMisproducedbyBcellsand,whenboundtoapathogen, willspurotherantibodies
andimmunecellsintoaction.

26. 5) Immunoglobulin E (IgE):
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ImmunoglobulinE(IgE) istheantibodyresponsiblefortheallergic
responsethatismostlyfoundinthelungs,skin,andmucosalmembranes.
Function:WhenIgEbindstoanallergen,ittriggersacascadeofevents.
Basophils and mast cells whicharesubtypesofWBCs, de-granulate
(break open) and release histamine which is an inflammatory
compound,intothebloodstream.Itishistaminethatisresponsibleforthe
symptomsofallergy.

27. Memorycellslivelong-termafteran
infectionhasresolvedandthey
quicklyexpandtoalargenumberof
effectorcellsonthere-exposureof
thedisease.
Duetomemorycellslargenumbersof
antibodiesareproducedifpast
infectioninvadesthebody.B-cells
andT-cellsplayaveryimportantrole
inmemoryimmuneresponse.
12. ROLE OF MEMORY CELLS IN IMMUNE
RESPONSE :
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28. • IMMUNOLOGICAL TOLERANCE:
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ImmunetolerancecanbedefinedasastateinwhichaTcellcannolonger
respondtoantigen.Immunetoleranceisastateofunresponsiveness to a
specificantigenorgroupofantigenstowhichapersonisnormally
responsive.Immunetoleranceisachievedunderconditionsthatsuppress
theimmunereactionandisnotjusttheabsenceofanimmuneresponse.
WHATISSPECIFICITYINIMMUNESYSTEM?
Specificityreferstotheimmunesystem'sabilitytotargetspecific
pathogens,andmemoryreferstoitsabilitytoquicklyrespondtopathogens
towhichithaspreviouslybeenexposed.
Specificimmuneresponsesaretailoredtoparticularpathogen.

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13.

30. 14. HYPERSENSITIVITY:
Hypersensitivity(alsocalledhypersensitivityreactionorintolerance)refersto
undesirablereactionsproducedbythenormalimmunesystem,includingallergiesand
autoimmunity.Theyareusuallyreferredtoasanover-reactionoftheimmunesystem
andthesereactionsmaybedamaging,uncomfortable,oroccasionallyfatal.
Therearefourtypesofhypersensitivitytheseinclude:
TYPE1.ReactionmediatedbyIgEantibodies
TYPE2.CytotoxicreactioniatedbyIgGorIgMantibodies
TYPE3.Reactionmediatedbyimmunecomplexes
TYPE4.Delayedreactionmediatedbycellularresponse.
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31. 15. DIFFERENCE BETWEEN IMMEDIATE AND
DELAYED HYPERSENSITIVITY:
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