ABSTRACT
ThehumanABO,H,andLewisbloodgroupdeterminantswereinitiallydefinedwithserological techniques,inthecontextofinvestigatinggeneticpolymorphismsintheexpressionofthese antigens,andtheirrolesinmediatingredbloodcelldestruction.Sincethediscoveryofthese determinantsearlierinthiscentury,thestructuralnatureofthesemolecules,andthegeneticbasis forpolymorphismintheirexpression,havebeenthesubjectofintensestudy.Theseinvestigations haveyieldedaratherhighresolutionpictureofthechemicalnatureofthesemoleculesandtheir biosyntheticpaths,andtheyhaveyieldedconsistenthypothesesconcerningthenatureofthegenes thatdeterminetheexpressionofthesestructures.Aswillbediscussedindetailbelow,theA,B, H,andLewisbloodgroupactiveantigensarenowknowntobeoligosaccharidemoleculeswhose synthesisiscatalyzedbythesequentialactionofenzymesknownasglycosyltransferases.Recent investigativeactivitiesinthisfieldhavecenteredontheisolationandcharacterizationofthegenes thatencodetheseenzymes.Theseeffortshavebeensuccessfulinseveralinstances;suchgenetic sequencesrepresenttoolsthatarenowinuseinstudiesdesignedtodefinethemolecularbasisfor theexpressionpatternsoftheseoligosaccharide-basedbloodgroupsandtodefinethegenetic basisforpolymorphismintheirexpression.
