Post‐transfusion Purpura: a Serological and Immunochemical Study

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Abstract
By applying the platelet suspension immunofluorescence test (PSIFT), platelet-specific alloantibodies responsible for post-transfusion purpura (PTP) were detected in 8 patients within a period of 2 yr. All patients were female and had previously received blood or had been pregnant. The platelet-specific alloantibodies had the specificity anti-Zwa in all the patients, who were all Zw(a.sbd.). In 2 patients the platelets were tested in the acute phase of the disease and found to be coated with IgG. In 1 patient an ether eluate was prepared from the platelets that reacted strongly with Zw(a+) platelets, but weakly with platelets from Zwb- homozygous individuals. The sera of these patients, and of 2 others whose platelets were not directly tested, taken in the acute phase of the purpura, reacted strongly with Zwa-positive platelets. The 4 sera also reacted, however weakly, with Zwa-negative platelets, with autologous platelets taken during remission and with platelets from patients with Glanzmann''s disease. Zwa.sbd.anti.sbd.Zwa complexes, present in the eluate and the sera, probably caused the reaction with Zwa-negative platelets and the patients'' own platelets. Immunochemical characterization of the post-transfusion purpura antibodies showed that in all patients these were IgG, in 2 combined with IgM antibodies. Antibodies of the sub-class IgG1 were found in all patients, sometimes together with IgG3. In the indirect immunofluorescence test with anti-complement serum, the PTP antibodies in only 4 sera were able to fix complement. In only 2 of these sera were these complement-binding antibodies detectable in the 51Cr-lysis technique and then in a much lower titer than in the immunofluorescence technique.