英国纽卡斯尔大学 生理学课件003

[e-mail]upsAcomplexmixtureofglycoproteinsandglycolipidsarefoundonthesurfaceofredbloodcells.Thusifanindividualisexposedtomoleculesthatarenoton‘self’RBCtheywillhavethecapacitytomountanimmuneresponsetothe‘foreign’,glycolipidsandproteins.Theexpressionpatternofthesemoleculesvariesbetweenindividuals.Amoleculethatcaninduceanimmuneresponseistermedanantigenandthusthesemoleculesaretermedredbloodcellsurfaceantigens.Thereare30humanbloodgroupsystemsandover600differentbloodgroupantigenshavebeendescribed.Ancompletebloodgroupisdescribedasthesetof29RBCsurfaceantigensofthesurfaceofanindividualsRBC.UsuallyonlytheABObloodgroupsystemandthepresenceorabsenceofRhesusDantigen(Rhesusfactor)aredeterminedtodescribebloodtype.BloodGroupsBloodgroupsareinheritedandrepresentcontributionsfrombothparents.TheABOSystemTheABOsystemiscontrolledbythegenesA,B,Handh.HisdominantandcodesforafucosyltransferaseenzymethatconvertsaprecursorsubstanceinRBCstoHSubstance(Hsubstanceisaglycoprotein).ThereforeHHindividualsmakeHsubstanceHhindividualsmakeHsubstancehhindividualsdoNOTmakeHsubstancehh(Oh)individualsTheseindividualsaredescribedashavingtheBombayphenotype.Note:Theyareveryrareinthepopulation(1/2500000)exceptinpartsofIndia(1/8000).TheseindividualsmaypossestheAorBgenebutasnoprecursorsubstanceHismadetheywillnothaveanyABOantigens.ThereisnoilleffectbutpeoplewiththisbloodgroupmustonlyhavetransfusionsfromotherindividualswiththisbloodgroupTheAandBallelesThesecodeforthetransferaseenzymes:A-transferase(N-acetylgalactosaminetransferase)orB-transferase(galactosetransferase)TheseenzymestransfersugarmoleculestoHsubstance:HsubstanceATransferaseAsubstanceHsubstanceBTransferaseBsubstanceAtransferaseonlymakesAsubstanceBtransferaseonlymakesBsubstanceTheAandBallelesAandBsubstancedifferonlyinthesugarmoleculethatisaddedtothegalactoseontheglycoproteinH-substancewithAtransferaseaddingN-acetylgalactosamineandBtransferaseaddinggalactose.TheAandBallelesSomeindividualspossesbothAandBtransferasesandthusaddeithergalactoseorN-acetylgalactosaminetothegalactoseontheglycoproteinH–substance.FortheABallelesindividualsmaybegenotypeAA–makeAsubstanceonlyAO–makeAsubstanceonlyBB–makeBsubstanceonlyBO-makeBsubstanceonlyAB-makeAandBsubstanceOO-makeHsubstanceonlyTheAandBallelesBloodGroupGenotypeRBCsubstancemadeAAAAsubstanceAOBBBBsubstanceBOABABAandBsubstanceOOOHsubstanceTheAandBallelesAandBBloodGroupsGroupFrequencyintheUKFrequencyinBengalisFrequencyinFinnsA42%44%24%B9%17%38%AB3%8%16%O46%31%22%ABBloodGroupsA,BandHsubstancesareglycoproteinsandanindividualcanraiseanimmuneresponseagainstthesemoleculesi.etheyareantigens.IndividualsthatdonothaveAorBsubstancesontheirRBCswilldevelopantibodiesagainsteitherorbothwithouteverhavingbeenexposedtobloodthatcarriestheseantigens.AandBsubstancesarewidespreadinnature(includinggutbacteria)andsoindividualsraiseantibodiesagainstthemsoonafterbeingborn.BloodGroupGenotypeAntigensAntibodiesinbloodinbloodAAAAsubstanceAOBBBBsubstanceBOABABAandBsubstancenoneOOOHsubstanceandABOBloodGroupsNotethatbloodgroupantigensarealsoknownasagglutinogensandtheantibodiesraisedagainstthemareknownasagglutinins.WhentheplasmaofbloodgroupAindividualismixedwiththeRBCsofabloodgroupBperson,thebantibodiesintheplasmacauseclumping(agglutination)oftheRBCs.ABOBloodGroupsClinicalrelevanceofABOgroupsThedonatedbloodwillobviouslyalsocontainantibodiesthatcouldpotentiallyagglutinatetherecipient’sRBCs.Howeverclinicallythisisoflesssignificancebecausethedonatedblood(andhenceantibodies)arequicklydilutedbytherecipient’sblood.TheRBCsofblooddonatedtoanindividualwillallagglutinateandeventuallylyseiftherecipientcontainsantibodiesagainstthem(thisisknownasahaemolytictransfusionreaction).ClinicalRelevanceofABOgroupsHowever:PersonswithBloodGroupABare‘universalrecipients’.TheycanreceivebloodofanyABOgroupwithoutdevelopingahaemolytictransfusionreaction.PersonswithBloodGroupOare‘universaldonors’.Theirbloodcanbegiventoanyotherwithoutdevelopingahaemolytictransfusionreaction.Becausemismatchingofbloodgroupswillresultinahaemolytictransfusionreaction,donatedbloodisalwayscorrectlymatchedbeforeanytransfusion.TheRhesusGroupThereareanumberofrhesusantigenswhichmaybepresentonRBCbutthemostcommonandmostimportantistheDantigen(agglutinogen).ApartfromtheABOsystem,thoseoftheRhesus(Rh)systemareofthegreatestclinicalrelevance.Theyarenamedaftertherhesusmonkeyinwhichtheywerediscovered85%ofCaucasians(99%Asians)havetheDantigenontheirRBCs(Rh+ve).15%ofCausasianspeoplelacktheD-antigenontheirRBCs(Rh–ve).Anti-RhDantibodiesarenotnormallyproducedbysensitisationtoenvironmentalantigens.RhesusAntigensDuringbirththereisoftenleakageofthebabiesRBCintothemotherscirculation.IfthebabyisRh+veandthemotherisRh-vetheredcellswillcausethemothertodevelopantibodiestotheDantigen.TheseantibodiesarenormallyoftheIg