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genes”;theircurrentdesignationashistocompatibility-2(H-2)geneswasinreferencetoGorer’sgroupIIblood-groupantigens.AlthoughGorerdiedbeforehiscontributionswererecognizedfully,SnellwasawardedtheNobelprizein1980forthiswork.TheMHCEncodesThreeMajorClassesofMoleculesThemajorhistocompatibilitycomplexisacollectionofgenesarrayedwithinalongcontinuousstretchofDNAonchromosome6inhumansandonchromosome17inmice.TheMHCisreferredtoastheHLAcomplexinhumansandastheH-2complexinmice.Althoughthearrangementofgenesissomewhatdifferent,inbothcasestheMHCgenesareorganizedintoregionsencodingthreeclassesofmolecules(Figure7-1):IClassIMHCgenesencodeglycoproteinsexpressedonthesurfaceofnearlyallnucleatedcells;themajorfunctionoftheclassIgeneproductsispresentationofpeptideantigenstoTCcells.chapter7IGeneralOrganizationandInheritanceoftheMHCIMHCMoleculesandGenesIDetailedGenomicMapofMHCGenesICellularDistributionofMHCMoleculesIRegulationofMHCExpressionIMHCandImmuneResponsivenessIMHCandDiseaseSusceptibilityMajorHistocompatibilityComplexEpossessesatightlylinkedclusterofgenes,thema-jorhistocompatibilitycomplex(MHC),whoseproductsplayrolesinintercellularrecognitionandindis-criminationbetweenselfandnonself.TheMHCpartici-patesinthedevelopmentofbothhumoralandcell-mediatedimmuneresponses.Whileantibodiesmayreactwithantigensalone,mostTcellsrecognizeantigenonlywhenitiscombinedwithanMHCmolecule.Furthermore,becauseMHCmoleculesactasantigen-presentingstruc-tures,theparticularsetofMHCmoleculesexpressedbyanindividualinfluencestherepertoireofantigenstowhichthatindividual’sTHandTCcellscanrespond.Forthisreason,theMHCpartlydeterminestheresponseofanindividualtoantigensofinfectiousorganisms,andithasthereforebeenimplicatedinthesusceptibilitytodiseaseandinthedevel-opmentofautoimmunity.TherecentunderstandingthatnaturalkillercellsexpressreceptorsforMHCclassIantigensandthefactthatthereceptor–MHCinteractionmayleadtoinhibitionoractivationexpandstheknownroleofthisgenefa...