Studies on the suppressor T cell function in patients with autoimmune thyroid diseases

Abstract

Suppressor T cell function induced by concanavalin A (con A) was evaluated in patients with Graves' disease and Hashimoto's thyroiditis. Patients with Graves' disease were divided into the following two groups: (1) untreated, and (2) euthyroid during antithyroid drug (methylmercaptoimidazole) therapy. T cells (2 X 10(5)), activated by con A for 48 hours, were added to preincubated responder cells (2 X 10(5)) and re-incubated for 7 days in the presence of pokeweed mitogen (PWM). IgG produced in the culture medium was measured by radioimmunoassay and then % suppressions (IgG) were calculated. Thyroid stimulating activity (TSA) in serum was measured by McKenzie's method by means of normal human thyroid slices, and % suppressions (c-AMP) were calculated. IgG produced in lymphocyte culture medium was suppressed by added con A-activated cells in untreated and euthyroid groups of Graves' disease, Hashimoto's thyroiditis and normal controls. The value of % suppression (IgG) was reduced in each group of Graves' disease compared to normal controls. No significant relation was observed between TSA in serum and % suppression (IgG), but three cases with high serum TSA showed low % suppressions (IgG). In 12 cases of Graves' disease, % suppression (IgG) had a positive relation with % suppression (c-AMP) in same medium. The amount of c-AMP produced in thyroid slices incubated in medium, in which responder cells (8 X 10(5)), was elevated in all 7 untreated cases of Graves' disease, while not elevated in 7 euthyroid cases. The value of % suppression (c-AMP) in euthyroid cases with Graves' disease was significantly higher than that in untreated cases. The value of % suppression (IgG) was reduced and had a significant negative relation with logarithm of serum antimicrosomal antibody titer in patients with Hashimoto's thyroiditis. These results indicate that low activity of suppressor T cell had a role on antibody production, including thyroid stimulating antibody, and pathogenesis of autoimmune thyroid diseases.