Elevation of platelet associated antibody levels in patients with chronic idiopathic thrombocytopenic purpura expressing the B8 and/or DR3 allotypes
Histocompatibility Antigens Class II
The HLA type DR3 was present in 11 of 26 patients with Chronic Idiopathic Thrombocytopenic Purpura (ITP), a significantly increased frequency (p less than 0.05). Levels of platelet associated immunoglobulin M(PAIgM) were significantly higher in the B8 and/or DR3 positive group of chronic ITP patients than in the B8 DR3 negative patients despite similar clinical outcomes. Other immunologic parameters assessed, including serum immunoglobulin levels, rate of catabolism of transfused IgG, and antibody coated autologous red cell clearances were similar for both groups. These results suggest that there is an immunobiologic abnormality associated with the B8 DR3 allotypes which may result in a predisposition not only to chronic ITP, but also to a significant increase in PAIgM. These results are in accord with studies linking autoantibody with B8 DR3.