Human platelet alloantigen (HPA)5a/b mismatch decreases disease-free survival in unrelated bone marrow transplantation

Matching of human platelet alloantigen (HPA) systems 2-6 was retrospectivel y investigated in 715 unrelated bone marrow transplantations. Of the five H PA systems studied, HPA-5 mismatching was found to have a significant effec t on the disease-free survival rate of recipients following transplantation in the HLA-A, -B, -C, and -DR allele-matched donor-recipient pairs. The ef fect of the HPA-5 mismatch was most significant in the recipient group poss essing the HLA haplotype A*2402-B*5201, which is a highly frequent haplotyp e among the Japanese population. However, the probability of development of acute graft-versus-host disease (GVHD) was not increased significantly by the HPA-5 mismatching. These findings suggest that the HPA-5 mismatching de creases the recipient's survival by a mechanism different from that in the case of mismatching of minor antigens found often in transplant recipients developing GVHD.