Platelet alloantigen frequencies in Caucasians: a serological study

Summary. Alloimmunization against platelet antigens is related to neonatal alloimmune thrombocytopenia and post‐transfusion purpura. Moreover, platelet‐specific alloantibodies, in addition to HLA‐specific antibodies, play a role in the state of refractoriness to platelet transfusions. Most platelet‐specific alloantigens have been assigned to platelet glycoproteins IIb/IIIa, Ib/IX and Ia/IIa. Data on antigen frequencies were first reported for Caucasians, but since then platelet glycoprotein polymorphisms have been reported for other populations, e.g. the Yuk alloantigens in Japanese. As information on the distribution of the recently described alloantigens is incomplete in Caucasians, this study was undertaken to provide reliable data on the PIA, Ko, Bak, Yuk and Br (HPA 1–5) alloantigens, of the ‘low‐frequency’ Sra and Vaa antigens and of the Naka isoantigen. In contrast to the frequencies determined in Oriental populations, all 964 individuals tested in this study were Yuka‐negative and all persons tested (n= 382) had Naka‐isoantigen‐positive platelets. A comparison of typing results shows that the recently described Siba‐alloantigen is identical with the Koa antigen.