Some evidence for the in vivo functional activation of suppressor T cells in asymptomatic patients with hemophilia A receiving Factor VIII concentrates.

Of 14 asymptomatic hemophilia A patients receiving factor VIII concentrates, 11 severe hemophilia patients had an inverted T-helper/suppressor ratio but 3 moderate patients had a normal ratio. Most hemophilia patients showed poor lymphocyte proliferative responses to mitogens and diminished in vitro immunoglobulin-producing ability of lymphocytes. One important finding was that most patients were found to have increased numbers of Ia-like antigen-positive suppressor T cells, suggesting that circulation activated suppressor T cells. In addition, OKT8+ suppressor T cells from severe hemophilia patients showed strong suppressor activity on B-cell differentiation in a Nocardia delipidated cell mitogen-driven system, whereas those from normal age-matched controls showed no suppressor function. These results suggested that suppressor T cells in hemophilia patients treated with factors might be already activated in vivo by undetermined mechanisms, implying the presence of a peculiar immunoregulatory status in this disease.