INFLUENCE OF HPA-1A AND HLA ANTIBODIES ON PRIMARY HEMOSTASIS

The influence of platelet specific and HLA antibodies was investigated on primary hemostasis by the in vitro bleeding test (IVBT) (Thrombost at 4000). Seven of 12 plasmas with HPA-1a (P1(A1)) antibodies and two with antibodies against glycoprotein Ib/IX significantly inhibited the IVBT of normal, cross-match-positive donor blood. This correlated wit h a significant increase of GMP-140 (CD 62) on the platelets, determin ed by flow cytometry. These results agree with the literature showing both activation and inhibition of platelet function by platelet specif ic antibodies. On the other hand, HLA antibodies showed a similar plat elet activation (shortening of occlusion time and decrease in blood vo lume in the IVBT, increase of CD 62 expression) as plasma samples of p olytransfused thrombocytopenic patients without HLA antibodies. It can be concluded that neither an activating nor an inhibitory effect of H LA antibodies on platelet function is significant in vivo. The IVBT se ems not to be suited for compatibility testing.