Spontaneous thyroiditis in thymectomized and irradiated Wistar rats.

Thyroiditis and autoantibodies to thyroglobulin were found to develop spontaneously in 60% of randomly bred Wistar rats subjected to thymectomy and whole body irradiation after weaning. Antinuclear antibodies were found in approximately 10% of these animals. Thyroiditis was seen in rats which were whole body irradiated without thymectomy but at a much lower incidence (22%). Control rats given irradiation to the thyroid region alone showed no such effects. The histology of the thyroid gland was similar to that seen in Hashimoto thyroiditis in man. The majority of rats which developed severe thyroiditis were found to be lymphopenic and to have negligible mitogenic responses to phytohaemagglutinin as well as other changes which in view of the thymectomy and irradiation may be considered to be indicative of impaired T cell function. It is concluded that these findings support the hypothesis that thymus-derived lymphocytes play an important part in the control of organ specific autoimmune disease.