Prevention of autoimmune thyroiditis in T cell-depleted rats by injections of crude thyroid extract.

The effect of intraperitoneal injections of crude allogeneic thyroid extract on the development of autoimmune thyroiditis in PVG/c rats subjected to thymectomy and repeated sublethal irradiation has been examined. Treatment with rat thyroid extract during the course of irradiation and before the onset of thyroiditis prevented the expected development of thyroid lesions and autoantibodies to thyroglobulin in these animals. Rats treated with crude rat liver extract under the same conditions developed thyroid disease similar to that of untreated controls. Treatment of thymectomized and irradiated rats with thyroid extract after the completion of the irradiation schedule failed to reduce the incidence and severity of thyroiditis in these animals as compared to that of untreated controls. The possible significance of these findings in relation to the pathogenesis of autoimmune thyroiditis in T cell-depleted rats is discussed.