免疫系统2.ppt
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免疫系统2.ppt
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,THEIMMUNESYSTEM,TheimmunesystemisabodywidenetworkofcellsandorgansthathasevolvedtodefendthebodyagainstattacksbyforeigninvadersThepropertargetsoftheimmunedefensesareinfectiousorganismsBacteriasuchasthesestreptococci;FungiParasites,includingtheseworm-likemicrobesthatcauseschistosomiasisVirusessuchasthisherpesvirus,Theorgansoftheimmunesystemarestationedthroughoutthebody.Theyareknownaslymphoidorgansbecausetheyareconcernedwiththegrowth,development,anddeploymentoflymphocytes-whitebloodcellsthatarekeyoperativesoftheimmunesystem.,OrgansoftheImmuneSystem,Theorgansoftheimmunesystemareconnectedwithoneanotherandalsowithotherorgansofthebodybyanetworkoflymphaticvesselssimilartobloodvessels.Immunecellsandforeignparticlesareconveyedthroughthelymphaticsinlymph,aclearfluidthatbathesthebodystissues.Lymphnodesaresmall,bean-shapedstructuresthatarelacedthroughoutthebodyalongthelymphaticroutes.Lymphnodescontainspecializedcompartmentswhereimmunecellscongregate,andwheretheycanencounterantigens.,LymphaticSystem,Cellsdestinedtobecomeimmunecells,likeallbloodcells,ariseinthebonemarrowfromso-calledstemcells.Somedevelopintomyeloidcells,agroupofwhitebloodcellsknownasphagocytes;phagocytesincludemonocytes,macrophages,andneutrophils.Othermyeloiddescendantsbecomegranule-containinginflammatorycellssuchaseosinophilsandbasophils.Lymphoidprecursorsdevelopintothesmallwhitebloodcellscalledlymphocytes.ThetwomajorclassesoflymphocytesareBcellsandTcells.,CellsoftheImmuneSystem,Atleasttwotypesoflymphocytesarekillercells-cytotoxicTcellsandnaturalkillercells.Toattack,cytotoxicTcellsneedtorecognizeaspecificantigen,whereasnaturalkillerorNKcellsdonot.Bothtypescontaingranulesfilledwithpotentchemicals,andbothtypeskilloncontact.Thekillerbindstoitstarget,aimsitsweapons,anddeliversaburstoflethalchemicals.,NaturalKillerCells,1.ImmunityThebodyscapabilityofresistingalltypesoforganismsandtoxinsthatmaydamagethetissuesororgansTwotypesofimmunityinnateimmunityandacquiredimmunityA.Innate(natural)immunitysurface-protectivemechanismsSkinmucousmembranesassociatedsecretions:
acidityofskin,vagina,sweat,sebum,stickymucus,salivalysozyme,anenzymethatdigeststhecellwallofmanybacteria,interferonsinterfereswithviralreplicationsecretedbyvirusinfectedcellsactivateothermacrophagesandNKcellscomplement20plasmaproteins,inactiveincirculationcomplementarytootherinternaldefensemechanisms4biologicalfunctionsactivationprocessclassicpathwayalternatepathway,Thecomplementsystemconsistsofaseriesofproteinsthatworktocomplementtheworkofantibodiesindestroyingbacteria.Complementproteinscirculateinthebloodinaninactiveform.Theso-calledcomplementcascadeissetoffwhenthefirstcomplementmolecule,C1,encountersantibodyboundtoantigeninanantigen-antibodycomplex.Eachofthecomplementproteinsperformsitsspecializedjobinturn,actingonthemoleculenextinline.Theendproductisacylinderthatpuncturesthecellmembraneand,byallowingfluidsandmoleculestoflowinandout,doomsthetargetcell.,Complement,BiologicalEffectsofComplementPerforatesplasmamembraneofpathogens:
Bacteria,EnvelopedViruses,Fungi,SomeNeoplasticCellsOpsonizes(Coats)ImmuneComplexesandPathogensPromotesClearanceofC3bOpsonizedTargetsByMacrophagesByErythrocyteTransporttoLiverandSpleenStimulatesInflammatoryResponses(Anaphylotoxins)ActivatesandAttractsLeucocytesAltersVascularPermeabilityPromotesSmoothMuscleContraction,inflammationbodysprotectiveresponsetoinjuryorinfectionfoursigns:
redness,edema,fever,painphagocytosisneutrophilsmonocytes/macrophagesnaturalkillercells(NK)?
B.Acquiredimmunityspecificallyrecognizespathogens(antigens),verypreciseeliminatespathogensimmunityissystemicMemoryantigenslargemolecules(protein,glycoproteins,polysaccharides,etc.mwt8,000)hapten=incompleteantigenantibodiesglycoproteinscalledimmunoglobinsstructurestwocomponents:
cell-mediatedimmunityandhumoralorantibody-mediatedimmunity,ImmunoglobulinsG,D,andEaresimilarinappearance.IgG,themajorimmunoglobulinintheblood,isalsoabletoentertissuespaces;itworksefficientlytocoatmicroorganisms,speedingtheiruptakebyothercellsintheimmunesystem.IgDisalmostexclusivelyfoundinsertedintothemembraneofBcells,whereitsomehowregulatesthecellsactivation.IgEisnormallypresentinonlytraceamounts,butitisresponsibleforthesymptomsofallergy.IgA-adoublet-concentratesinbodyfluidssuchastears,saliva,andthesecretionsoftherespiratoryandgastrointestinaltracts.Itis,thus,inapositiontoguardtheentrancestothebody.IgMusuallycombinesinstar-shapedclusters.Ittendstoremaininthebloodstream,whereitisveryeffectiveinkillingbacteria.,Antibodies,cell-mediatedimmunityT-lymphocytes(Tcells)preparationofcompetentTcellsprecursorsofTcellsenterthymusglandsT4cells(possessingCD4)andT8(CD8)T4acquiresasurfaceproteincalledClassIIMHC(majorhistocompatibilitycomplex)T8acquiresclassIMHCnegativeselection(96-99%)-ApoptosisT-cellsandmacrophagescoordinatetheirdefensefunctionT4cellsdifferentiateintohelperandmemorycellsT8cellsdifferentiateintocytotoxicTcellsandsuppressorTcells,Attheheartoftheimmuneresponseistheabilitytodistinguishbetweenselfandnonself.Everybodycellcarriesdistinctivemoleculesthatdistinguishitasself.Normallythebodysdefensesdonotattacktissuesthatcarryaselfmarker;rather,immunecellscoexistpeaceablywithotherbodycellsinastateknownasself-tolerance.,ClassIMHC-MarkersofSelf,ActivationofTCells:
HelperandCytotoxic,CytotoxicTcell:
perforins/granzymes,Cytokines-diverseandpotentchemicalmessengerssecretedbythecellsoftheimmunesystem-andthechieftoolofTcells.Lymphokines-lymphocytes,includingbothTcellsandBcellsMonokines-monocytesandmacrophagesBindingtospecificreceptorsontargetcells,cytokinesrecruitmanyothercellsandsubstancestothefieldofaction.Cytokinesencouragecellgrowth,promotecellactivation,directcellulartraffic,anddestroytargetcells-includingcancercells.Becausetheyserveasamessengerbetweenwhitecells,orleukocytes,manycytokinesarealsoknownasinterleukins.,Cytokines/lymphokines,humoral-mediatedimmunityBlymphocytes(bursaofFavriciusinbirds)theliverandbonemarrowpreprocessBcellsBcellsandmacrophagescoordinatetheirdefensefunctionactivatedBcellsdifferentiateintocloneplasmacellsandmemoryBcellsimportanceofhelperTcellsmechanismsofactionsofantibodiesdirectactionsagglutinationprecipitationneutralizationlysiscomplementsystemforantibodyaction,TheBcellusesitsreceptortobindamatchingantigen,whichitproceedstoengulfandprocess.Thenitcombinesafragmentofantigenwithitsspecialmarker,theclassIIprotein.ThiscombinationofantigenandmarkerisrecognizedandboundbyaTcellcarryingamatchingreceptor.ThebindingactivatestheTcell,whichthenreleaseslymphokines-interleukins-thattransformtheBcellintoanantibody-secretingplasmacell.,ActivationofBCellstoMakeAntibody,WheneverTcellsandBcellsareactivated,somebecomememorycells.Thenexttimethatanindividualencountersthatsameantigen,theimmunesystemisprimedtodestroyitquickly.Long-termimmunitycanbestimulatednotonlybyinfectionbutalsobyvaccinesmadefrominfectiousagentsthathavebeeninactivatedor,morecommonly,fromminuteportionsofthemicrobe.Short-termimmunitycanbetransferredpassivelyfromoneindividualtoanotherviaantibody-containingserum;similarly,infantsareprotectedbyantibodiestheyreceivefromtheirmothers(primarilybeforebirth).,Immunity:
Short-andLong-TermCellMemory,Whentheimmunesystemmalfunctions,itcanunleashatorrentofdisordersanddiseases.Oneofthemostfamiliarisallergy.AllergiessuchashayfeverandhivesarerelatedtotheantibodyknownasIgE.Thefirsttimeanallergy-pronepersonisexposedtoanallergen-forinstance,grasspollen-theindividualsBcellsmakelargeamountsofgrasspollenIgEantibody.TheseIgEmoleculesattachtogranule-containingcellsknownasmastcells,whichareplentifulinthelungs,skin,tongue,andliningsofthenoseandgastrointestinaltract.Thenexttimethatpersonencountersgrasspollen,theIgE-primedmastcellreleasespowerfulchemicalsthatcausethewheezing,sneezing,andothersymptomsofallergy.,DisordersoftheImmuneSystem:
Allergy,Sometimestheimmunesystemsrecognitionapparatusbreaksdown,andthebodybeginstomanufactureantibodiesandTcellsdirectedagainstthebodysowncellsandorgans.Suchcellsandautoantibodies,astheyareknown,contributetomanydiseases.Forinstance,Tcellsthatattackpancreascellscontributetodiabetes,whileanautoantibodyknownasrheumatoidfactoriscommoninpersonswithrheumatoidarthritis.,DisordersoftheImmuneSystem:
AutoimmuneDisease,Whentheimmunesystemislackingoneormoreofitscomponents,theresultisanimmunodeficiencydisorder.Thesecanbeinherited,acquiredthroughinfection,orproducedasaninadvertentsideeffectofdrugssuchasthoseusedtotreatcancerortransplantpatients.AIDSisanimmunodeficiencydisordercausedbyavirusthatdestroyshelperTcellsandthatisharboredinmacrophagesaswellashelper(T4)Tcells.TheAIDSvirussplicesitsDNAintotheDNAofthecellitinfects;thecellisthereafterdirectedtochurnoutnewviruses.,DisordersoftheImmuneSystem:
AIDS,
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