Evidence for thyroid antigen-reactive T lymphocytes infiltrating the thyroid gland in Graves' disease.

We have investigated the relative distribution and some in vitro functions of thyroid-infiltrating immunocompetent cells obtained at fine-needle aspiration biopsy in twelve patients with Graves' disease and thirteen patients with Hashimoto's thyroiditis. In both disorders the predominant (57--59%) thyroid-infiltrating cell was a small lymphocyte. Significant numbers of plasma cells (10%) were seen only in Hashimoto's thyroiditis. Mononuclear phagocytes (monocytes plus macrophages) were present in similar numbers (12--18%) in both disorders. In both Graves' and Hashimoto's disease there was a relative reduction of (thymus-dependent) lymphocytes in the thyroid gland as compared to the blood. Blood and thyroid-infiltrating T lymphocytes were tested for in vitro cell-mediated immunity (CMI) to thyroid antigen in the leucocyte migration inhibition test (LMT). CMI was readily demonstrated in the blood of most patients with Graves' and Hashimoto's disease. When the thyroid-infiltrating lymphocytes were tested for CMI in the LMT, only the infiltrating cells from patients with Graves' disease displayed CMI, whereas the thyroid-infiltrating lymphocytes in Hashimoto's disease were negative. Fractionation of the immunocompetent cells demonstrated that the thyroid antigen-induced LMT response of blood and thyroid-infiltrating lymphocytes in Graves' disease is a T lymphocyte-dependent phenomenon.