Functional Differences of Anti‐T‐Cell Antibody in Patients with Systemic Lupus Erythematosus and Ulcerative Colitis

The loss of suppressor T‐cell function results in an abundant production of autoantibodies in systemic lupus erythematosus (SLE). As a cause of this suppressor T‐cell defect, anti‐T‐cell antibody seems to be of prime importance. On the other hand. anti‐T‐cell antibodies can be detected in various other autoimmune diseases, but their functional characteristics have not been determined. In the present study, the functional characteristics of anti‐T‐cell antibody from a selected subgroup of patients with ulcerative colitis (UC) were compared with those from patients with SLE. Anti‐T‐cell antibody from the patients with SLE reacted with a T8 subset, resulting in a suppressor defect, whereas anti‐T‐cell antibody from the UC patients reacted primarily with a T4 subset. Functionally, SLE T cells failed to proliferate in response to concanavalin A. whereas UC⁻ T cells from UC patients failed to proliferate in response to phytohaemagglutinin. In the Ig synthesis system, both SLE⁻ and UC⁻ T cells increased Ig production of B cells. Since UC⁺ T cells did not contribute to the generation of Con‐A‐inducible suppressor activity, we believe that serum from the selected subgroup of patients with UC reacted with the inducer T‐cell subset.