The HL‐A System: Antigenic Heterogeneity and Four New Antigens

Abstract

Four new antigens of the second HL—A series are reported. They were established by means of lymphocytotoxic and platelet complement‐fixing antisera, and they behaved in population and family studies as determined by alleles at the second HL—A sublocus. It was found that three of them were parts of a previously assumed monofactorial antigen: SL. The antigen SL thus is heterogeneous, as also seems to be true of several other HL—A antigens. If all HL—A genetic determinants presently identified in our laboratories are taken into account, 18,145 different genotypes are possible. Implications of heterogeneous HL—A antigens for histocompatibility testing and matching are discussed.