Altered balance of immunoregulatory T lymphocyte subsets in autoimmune thyroid diseases.
Three monoclonal antibodies recognizing cell surface antigens of total peripheral (OKT3), helper/inducer (OKT4) and suppressor/cytotoxic (OKT8) T lymphocytes were used by an indirect immunofluorescence technique to enumerate peripheral T lymphocytes in 25 patients with Graves' disease (including 4 euthyroid Graves' patients), 16 patients with Hashimoto's thyroiditis and 22 normal controls. Total lymphocyte count and percentages of overall T and helper/inducer T cells among peripheral lymphocytes in these conditions showed no significant difference from those of the controls. Percentage of suppressor/cytotoxic T cells, however, was decreased in Graves' disease patients with or without hyperthyroidism. The ratio of helper/inducer T cells to suppressor/cytotoxic T cells was increased in Graves' disease population and slightly increased in hypothyroid Hashimoto's thyroiditis patients. The ratio correlated with the mitogenic response of peripheral mononuclear cells to phytohaemagglutinin, but not with the serum levels of thyroid hormones nor with the titres of thyroid autoantibodies. These findings are in accordance with the results of previous functional studies and indicate possible defects in suppressor T lymphocytes in autoimmune thyroid disease.