Autoreactive platelet antibody in post transfusion purpura.

Post transfusion purpura in a DR3, DRw52 positive, PlA1 negative woman rapidly responded to high-dose intravenous gammaglobulin therapy. Using the platelet immunofluorescence test (PIFT) high titre IgG and IgM alloantibodies were detected in the patient's acute serum. These alloantibodies had PlA1 specificity and the patient's serum produced a broad, 100 kDa band on Western Blot with PlA1 positive platelets. Acute phase serum also contained an IgG antibody which reacted in the PIFT with the patient's own platelets, and PlA1 negative platelets. When tested by Western Blot with PlA1 negative and Glanzmann's Thrombasthenia platelets, the acute serum produced bands at 180 and 200 kDa. The autoreactive antibody was not detected once the platelet count returned to normal. These findings provide evidence for the hypothesis that the mechanism of autologous platelet destruction in PTP is autoimmune.