The reactivity of human platelets in the 125I-labelled staphylococcal protein A test.

Stored platelets have been employed in the testing of various antiplatelet antibodies and platelet unrelated immune complexes. The antisera included sera containing ABO-,HLA- or platelet specific (ZWa) antibodies and serum from an adult patient with idiopathic thrombocytopenic purpura (ITP). Use was made of 125I-labelled staphylococcal protein A (IPA) for the detection of platelet bound IgG. The reactivity of cells with the ITP serum and sera from healthy blood donors increased after storage for a few days, and declined after a highly reactive period extending over some weeks. In some cases predilution of the serum increased the probability of discovering weak antibodies. The normal components of the serum modified the platelet-antibody reaction, but all the various kinds of platelet reactive activities could be detected by this single test.