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 antigens is important to the improvement of diagnosis and genetic counseling and to the development of screening programs for women at risk of having babies with neonatal alloimmune thrombocytopenia. Description of the immunogenetics of the human platelet antigens in some racial groups has been incomplete. Study Deign and Methods: A reverse dot blot technique employing polymerase chain reaction-amplified genomic DNA was applied in genotyping the five major human platelet antigens in the following populations: 100 African American and 100 white women admitted to the obstetric unit at Johns Hopkins Hospital (Baltimore, MD) and 100 inpatients at Yohsei University (Seoul, Korea). Results: The gene frequencies of HPA-2b (Ko(a)) and HPA-5b (Br-a) in African Americans were twice those in whites (African Americans: 0.18 and 0.21, respectively; whites: 0.09 and 0.11, respectively). There is a very low gene frequency of the HPA-1b (PIA2) allele in Koreans (0.005). No significant differences were found in the gene freqencies of the human platelet antigens in whites in this series and those in published European studies. Conclusion: These studies indicate a higher potential risk for alloimmunization to HPA-2 (Ko) and HPA-5 (Br) antigens in African Americans than in whites. In addition, the low gene frequency of HPA-1b (PIA2) in African Americans and Koreans suggests that alloimmunization to HPA-1a (PIA2) would be very unusual in these populations. These data may provide the basis for planning neonatal alloimmune thrombocytopenia screening programs in certain ethnic populations.