ABSTRACT
AutoimmuneHemolyticAnemia499
thatanantibody,suchasanti-Kpb,maybefoundinapatient'sserumandthepatient'sRBCs foundtolackortohaveaweakenedexpressionoftheputativeantigen;forinstance,theKpb antigen.ThiscanoccurwhenthepatienthasanegativeorweaklypositiveDAT;thusallresults seemtoindicateanalloantibody.Laterinthecoursewhenthepatient'shemolyticanemiais inremission,andtheantibodyisnolongerintheserum,thepatientcannowbeshownto possesstheantigeninnormalstrength,andtheoriginalstoredserumnowreactswiththe patient'sRBCs,suggestingthattheantibodyisreallyanautoantibody.Manyspecificitieshave beenassociatedwiththisphenomenon(Rh,LW,Kell,Ge,An/Wj,Duffy,Kidd,Ena,Co, Scl).Onehastobelievethatitismuchmorecommonthanthenumberofreportsreflectsas itisnotcommontorecheckantigenstatusandretesttheoriginalserummonthsaftertheinitial tests.Therearesomedataintheliteraturethatsuggestthisphenomenonrightnotberestricted toAIHA.In1984,SalamaandMueller-Eckhardt(26)publishedaprovocativepaperconcerning delayedtransfusionreactions,inwhichtheypresentedfindingsthatdifferedconsiderablyto whatwehadbeenteachingourstudentsforyears.Oneofthemostinterestingfindingswas thattheDATremainedpositiveforover97daysinsixorsevencasesfollowedfor312days. Anti-KcouldbeelutedfromtheRBCsofonepatientfor299daysfollowingtransfusion.The antibodyelutedofftheRBCsofallthesecaseshadaspecificitysimilartotheoriginalserum alloantibody,yetnoantigen-positivetransfusedcellscouldpossiblyhavebeenpresentatthis time.In1990,NessdescribedverysimilarfindingsintheUnitedStates(27).Thus,antibodies suchasallo--anti-E,allo--anti-K,andallo--anti-Jkacanbeeluted,over100daysfollowing transfusion,fromDAT-positiveredcells,whicharepresumablythepatient'sownantigen negativeRBCs.Theseantibodiesareshowingthesamecharacteristicsasthemimicking antibodiesthatwefindassociatedwithAIHA.NeitherSalamaandMueller-Eckhardt(26)nor Nessetal.(27)triedadsorbingtheseantibodieswithantigen-negativeandantigen-positive RBCs.Iftheseantibodiesarenotadsorbedbyantigen-negativecells,thusfittingthedefinition ofalloantibodies,thenonehastoquestionwhytheyarepresentonthepatient'sownRBCs.
