Studies on the HLA Class-II Antigens of a Patient Presenting a Double Alloimmunization Following Posttransfusion Purpura.

In the Caucasian population, platelet incompatibility within the HPA-1 (PlA1/A2) and HPA-5 (Bra/b) alloantigen systems are the two most likely causes of post-transfusion purpura (PTP) and neonatal alloimmune thrombocytopenia. However, the way in which HLA (class-II) antigens participate in alloantibody formation is unclear. The patient (M-J.G.) is a middle aged woman with two children who developed a severe PTP (< 2000 platelets/µ1) 8 days after receiving red cell concentrates during coronary bypass surgery. During treatment with intravenous gamma-globulin and corticosteroids, her platelet count peaked, fell again, and returned to normal over a period of several months. Western blotting and/or the monoclonal antibody specific-immobilization of platelet antigens (MAIPA) assay performed with serum prepared at the height of her initial thrombocytopenia revealed antibodies to both the PlA1 and the Bra alloantigens. This rare combination prompted us to study the expression of specific HLA class II antigens in ...