GENE-FREQUENCIES OF THE 5 MAJOR HUMAN PLATELET ANTIGENS IN AFRICAN-AMERICAN, WHITE, AND KOREAN POPULATIONS

Background: The study of the immunogenetics of the human platelet anti gens is important to the improvement of diagnosis and genetic counseli ng and to the development of screening programs for women at risk of h aving babies with neonatal alloimmune thrombocytopenia. Description of the immunogenetics of the human platelet antigens in some racial grou ps has been incomplete. Study Deign and Methods: A reverse dot blot te chnique employing polymerase chain reaction-amplified genomic DNA was applied in genotyping the five major human platelet antigens in the fo llowing populations: 100 African American and 100 white women admitted to the obstetric unit at Johns Hopkins Hospital (Baltimore, MD) and 1 00 inpatients at Yohsei University (Seoul, Korea). Results: The gene f requencies of HPA-2b (Ko(a)) and HPA-5b (Br-a) in African Americans we re twice those in whites (African Americans: 0.18 and 0.21, respective ly; whites: 0.09 and 0.11, respectively). There is a very low gene fre quency of the HPA-1b (PIA2) allele in Koreans (0.005). No significant differences were found in the gene freqencies of the human platelet an tigens in whites in this series and those in published European studie s. Conclusion: These studies indicate a higher potential risk for allo immunization to HPA-2 (Ko) and HPA-5 (Br) antigens in African American s than in whites. In addition, the low gene frequency of HPA-1b (PIA2) in African Americans and Koreans suggests that alloimmunization to HP A-1a (PIA2) would be very unusual in these populations. These data may provide the basis for planning neonatal alloimmune thrombocytopenia s creening programs in certain ethnic populations.