中科院細(xì)胞與分子免疫學(xué)課程chapter8

中科院細(xì)胞與分子免疫學(xué)課程chapter8T淋巴細(xì)胞的成熟：祖T細(xì)胞，前T細(xì)胞，雙陽性階段，單陽性階段，成熟階段兩次選擇：1.陽性選擇：2.陰性選擇：Chapter8ActivationofTlymphocytesHowtoactivatetheTcell?

Inperipherallymphoidorgans,Na?veTlymphocytesrecognizeantigensandareactivated.Inlymphoidorgansorinnonlymphoidtissues,effectorTcellsrecognizeantigensandareactivated.TheactivationofTcellsrequiresa.antigenpresentedbyAPCb.costimulatorsc.cytokinesproducedbytheAPCsandbytheTcells.4a.Na?veTcellsrequireactivationbydendriticcells;4b.EffectorTcellscanrespondtoantigenspresentedbyawidervarietyofAPC.WhattheactivatedTcellscando?ProliferationDifferentiationintoEffectorCellsCD4+Tcell:Th1andTh2Th1:Stimulatecytokine(IL-12andIFN-g),secretecytokines:IL-2,INF-gandTNF-b.Th2:Stimulatecytokine:IL-4,secretecytokines:IL-4,5,6,10,13.CD8+TcelldifferentiateintofunctionalCTL.3.DifferentiationintoMemoryCells4.DeclineofTCellResponsesRoleofCostimulatorsinTCellActivationCostimulators:CD28:B7-1andB7-2TheexpressionofcostimulatorsisregulatedtomakesurethecorrecttimeandplaceexpressionTheexpressionofB7costimulatorsisincreased2a.bymicrobialproducts,2b.bycytokinesofinnateimmunity3.Maturedendriticcellsexpressthehighestlevelsofcostimulators.4.Adjuvantsareproductsofmicrobesthatstimulatetheexpressionofcostimulators.5.PreviouslyactivatedeffectorandmemoryTcellsarelessdependentoncostimulationbytheB7:CD28pathwaythanarena?vecells.RoleofCD40inTcellactivationActivatedTcellsexpressCD40LAPCsexpressCD40CD40LbindingtoCD40candeliversignalsthatenhancetheexpressionofB7costimulatorsontheAPCs.SecretionofcytokinesIL-12isincreaseduponCD40LinteractionwithCD40.SignalTransductionbytheTCRComplex1.Whatisthegoal:activatethetranscriptionofgenesthataresilentinna?vecells,theseproteinsmediatetheresponsesandfunctionsofactivatedTcells.2.Howissignaltransductiontriggered:byligationofmultipleantigenreceptorsandcoreceptors.3.Whathappenedaftersignaltransductionincell:clusteringofmembranereceptors,tyrosinephosphorylationofseveralprotein,andrecruitmentandactivationofadapterproteins.4.WhattheimportantbiochemicalpathwaysintheactivationofTcells:1)Ras-MAPkinasepathway2)theproteinkinaseCpathwayMajorstepsinsignalingbytheTCREarlymembraneevents:1.FormationoftheImmunologicalSynapse:

Immunologicalsynapse:theregionofphysicalcontactbetweentheTcellsandtheAPCTcellcomponentsparticipatedinare:TCRcomplex,coreceptors(CD4orCD8),CD28,theenzymesandadaptorproteins.Theformationistriggeredbyantigenrecognition4)BringssignalingmoleculesintoproximitytooneanotherTheformationofsynapsewasdemonstratedbyconfocalmicroscopy.2.ActivationofTyrosineKinasesTyrosinesresiduesin:CD3,zchain.Tyrosinekinases:Lck,thatisassociatedwiththecytoplasmictailsofCD4andCD8.Fyn,anothertyrosinekinaseinphysicalassociationwiththeCD3molecules.ZAP-70,attachedtothetyrosinephosphorylatedITAMszchain.ZAP-70isonlyexpressedinTandNKcells.2.ActivationofTyrosineKinasesProcedure:Lckisactivatedbyautophosphorylation,thentheactiveLckphosphorylatesthetyrosinesintheITAMoftheCD3andthezchainZAP-70bindingtotwophosphorylatedtyrosineresiduesofeachITAMsinthezchainLckphosphorylatesthetyrosinesofZAP-70.ZAP-70acquiresitsowntyrosinekinaseactivity.MultipleZAP-70couldberecruitedtothemultiplephosphorylatedITAMs.3.RecruitmentandActivationofAdapterProteinsAdapterproteinsbringthesignalingmoleculesintospecificcellularcompartments.Canbindotherproteins.ZAP-70phosphorylatedtyrosinesofLAT.ActivatedLATbindsphospholipaseCg1,SLP-76,andGrb-2.ServestobringavarietyofdownstreamcomponentsofTCRsignalingpathwaysclosetotheirupstreamactivators.Ras-MAPKinaseSignalingPathwaysinTlymphocytesProteinsthatwereneededinthepathway:1.Ras:amemberofafamilyof21-kDguaninenucleotide-bindingproteins,(smallGprotein)hasalotofactivationresponsesindifferentcelltypes.ThereasonisthatRascanrecruitoractivatevariouscellularenzymes.2.MAPkinases:ERK,extracellularreceptor-activatedkinaseJNK,c-JunN-terminalkinasealsocalledstress-activatedprotein.P38Ras-MAPKinaseSignalingPathwaysinTlymphocytesLATcanbindGrb-2,thentheGrb-2recruitstheRasGTP/GDPexchangefactor---Sos(sonofsevenless)SoscatalyzesGTPforGDPexchangeonRas.Ras.GTPactivatesmitogenactivatedprotein(MAP)kinases--ERKTheERKphosphorylatesaproteincalledELK,andstimulatestranscriptionofFos,TwootherMAPkinases:Rac.GTPactivatesJNK,JNKphosphorylatesc-Jun,anothercomponentoftranscriptionfactor.p38,istooactivatedbyRac.GTPandinturnactivatesvarioustranscriptionfactor.Pathway:Calcium-andproteinKinaseC-MediatedSignalingPathwaysinTlymphocytesPLCg1isrecruitedtophosphorylatedLAT,PLCg1isacytosolicenzymespecificforinositol（肌糖）phospholipids（磷脂質(zhì)）.PLCg1is

phosphorylatedbyZAP-70.PhosphorylatedPLCg1catalyzes

thehydrolysisofaplasmamembranephospholipidcalledPIP2（磷脂酰肌醇二磷酸）,generatingtwoproducts:IP3（三磷酸肌醇）andDAG（二酰基甘油）.SignalpathwayofIP3:IP3bindstothereceptorofERandstimulatesreleaseofmembrane-sequesteredcalciumstores.Calciumionconcentrationincreased,andbindingtoacalcium-dependentregulatoryproteincalledcalmodulin（鈣調(diào)蛋白）.Calcium-calmodulincomplexesactivatedcalcineurin（鈣調(diào)磷酸酶）thatisimportantfortranscriptionfactor.Calcium-andproteinKinaseC-MediatedSignalingPathwaysinTlymphocytesCalcium-andproteinKinaseC-MediatedSignalingPathwaysinTlymphocytesDAGishydrophobic,andremainsinthemembranewhereitisformed.TheelevatedfreecytosoliccalciumandDAGactivatesmembrane-associatedPKC（蛋白激酶C）.PKCqisoformlocalizestotheimmunologicalsynapse.PKCqactivatesthenucleartranslocationoftheNF-kBtranscriptionfactor.SignalpathwayofDAG:ActivationofTranscriptionFactorsthatRegulateTCellGeneExpressionTherequirementformultipletranscriptionfactorsaccountsfortheneedtoactivatemultiplesignaltransductionpathways.ForexampleIL-2:threefactors(NFAT,AP-1,NFkB)areneeded,andallthesitesmustbeoccupiedformaximaltranscriptionofIL-2gene.ThesethreefactorsarecriticalformostTcellresponses.ActivationofTranscriptionFactorsthatRegulateTCellGeneExpressionNFAT:AtranscriptionfactorrequiredfortheexpressionofIL-2,IL-4andothercytokines.FourtypesofNFAT,NFAT1and2inTcells.InrestingTcells,NFATpresentsinaninactive,serinephosphorylatedforminthecytoplasm.Itisactivatedbythecalcium-calmodulin-dependentphosphatasecalcineurin.CalcineurindephosphorylatescytoplasmicNFAT,uncoveringanuclearlocalizationsignal.ActivationofTranscriptionFactorsthatRegulateTCellGeneExpression2.AP-1Atranscriptionfactorfoundinmanycelltypes,andisspecificallyactivatedinTlymphocytesbyTCRmediatedsignals.ItiscomposedofFosandJun.FromtheErkandPKCpathway,Fosgenewasgenerated.JNKphosphorylatesc-Jun,Fosandphosphorylatedc-JunconsistedAP-1.ActivationofTranscriptionFactorsthatRegulateTCellGeneExpression3.NFkBAtranscriptionfactorthatisactivatedinresponsetoTCRsignalsandisessentialforcytokinesynthesis.InrestingTcells,NFkBis

presentinthecytoplasminacomplexwithainhibitorsIkB.AfterphosphorylationofIkB,ubiquitinattachtotheproteinandbedegraded.NFkBisreleasedandtranslocatedtothenucleus.抗原MHC復(fù)合體T淋巴細(xì)胞激活：共刺激信號細(xì)胞因子T淋巴細(xì)胞被激活佐劑免疫突觸形成T細(xì)胞內(nèi)信號轉(zhuǎn)導(dǎo)激活T細(xì)胞內(nèi)信號轉(zhuǎn)導(dǎo)激活：CD4分子上Lck自身磷酸化CD3分子ITAM酪氨酸基序磷酸化ZAP70結(jié)合ZAP70被磷酸化并且酪氨酸激酶活性激活多個ZAP聚集LAT蛋白被磷酸化LAT蛋白被磷酸化磷脂酶Cg1活化Grb-2活化PIP2IP3DAGPKCNFkBNFATERKELKFosJNKJUNAP-1BiochemistryofCostimulationCD28canactivateMAPkinasepathway,includingERKandJun.CanactivateNFkBtobind