[Effect of HPA-1a(PLA1) and HLA antibodies on platelet function, measured with the in vitro bleeding test]

The influence of platelet-specific and HLA antibodies on primary hemostasis was investigated by the in vitro bleeding test (IVBT). Seven of 12 plasmas with HPA-1a (PLA1) antibodies and two with antibodies against glycoprotein Ib/IX significantly inhibited the IVBT of normal cross-match-positive donor blood. This correlated with an increase of GMP-140 on the platelets determined by flow cytometry. Therefore the inhibition of the IVBT was interpreted to be due to rapid platelet activation by platelet-specific antibodies followed by an irreversible loss of function. In contrast, with HLA antibodies neither activation nor inhibition of the platelet function could be proven.