PERSISTENCE OF PLATELET ANTIBODIES IN VIVO AND FREQUENCIES OF PLATELET ANTIGENS AND CHANCE OF IMMUNIZATION, IN JAPANESE POPULATION

We detected 57 platelet antibodies (anti-HPA-4a:1, anti-HPA-4b:51, anti-HPA-5b:4, anti-Naka:1) in female donors' sera. We were able to collect information of the history of pregnancy and transfusion from 20 out of 57 female donors. One of them was found to have anti-HPA-4b in her serum 32 years after her last pregnancy. Testing platelets from random Japanese people with anti-HPA-2b, anti-HPA-3a, anti-HPA-4b, anti-HPA-5b and anti-Naka, we found that approximately 23.12per cent (132/571) of them were HPA-2 (b+), 81.78per cent (404/494) HPA-3 (a+), 2.76per cent (20/725) HPA-4 (b+), 3.90per cent (9/231) HPA-5 (b+) and 96.18per cent (605/629) Nak (a+), respectively. From these data, we calculated phenotype and gene frequencies of the platelet system. We examined five families of which the proposit had low-incidence phenotypes of platelet antigen systems, and found persons with more than two such phenotypes. Then, we calculated coexistence rate of such infrequent phenotypes in an individual. In one of the families studied, we came across anti-HPA-4b which was formed by a proposita's mother.