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Both 51Cr-survival studies with donor platelets and allogenic skin transplantations were performed in a patient with immune unresponsiveness to platelet antigens, i.e., HLA-and platelet-specific antigens. The patients, who suffered from hypoplastic anaemia, was successfully transfused with random donor platelets during 13 months. The serum of this patient contained only granulocyte-and mononuclear-cell-reactive antibodies, but no platelet-reactive antibodies. A nearly normal survival time of the donor platelets as well as a prolonged rejection time of a skin allograft of the same donor support the serological findings. The 51Cr-platelet survival time was not influenced by a leucocyte concentrate from the same donor, which was administered at the same time. Thus, in our patient, no increased platelet destruction could be induced via the so-called innocent bystander mechanism.

By lowering the pH of the medium, allo- and autoantibodies bound to granulocytes and platelets could be eluted from these cells and their presence in the eluate could subsequently be detected with normal donor granulocytes and platelets, respectively, in the immunofluorescence test and/or agglutination test. IgG- as well as IgM- and IgA-containing antibodies were detectable in the eluates. Depending on the attraction mechanism between antigen and antibody, some antibodies were also eluted by dimethylsulphoxide at pH 9.5, ether and/or by heating at 56 degrees C. By differential elution of antibodies from donor platelets, we demonstrated the simultaneous presence of platelet-specific antibodies and HLA antibodies in the serum of a mother whose newborn suffered from transient neonatal thrombocytopenia.