HLA antigens in idiopathic thrombocytopenic purpura.

The lymphocytes of 52 patients with the clinical diagnosis of idiopathic thrombocytopenic purpura (ITP) were typed for the HLA-A, -B and -C antigens, and of 27 of those patients also for the DR antigens. ITP proved not to be significantly associated with any of the HLA-A, -C or -DR antigens tested for. On the platelets of 35 of these 52 patients autoantibodies were detected in the direct immunofluorescence test. In these 35 patients with autoimmune thrombocytopenia (AITP), an increased frequency of HLA-Bw38 was found (14.3% versus 2.6% in controls). The frequency of none of the HLA antigens was significantly increased in the group of 17 ITP patients without demonstrable autoantibodies. The difference in association with HLA-Bw38 between AITP and ITP without demonstrable autoantibodies was not significant.