SPONTANEOUS DEVELOPMENT OF AUTOIMMUNE THYROIDITIS IN NEONATALLY THYMECTOMIZED MICE

Abstract

An experimental mouse model of autoimmune thyroiditis induced by neonatal thymectomy (between 2 and 4 days of age) is described. Thymectomy within 24 h after birth or thymectomy after 5 days of age failed to induce the disease. This type of thyroiditis occurred spontaneously a few months after the operation, lasted until approximately 12 mo. of age, and appeared to subside with aging. Hybrid mice of (C3H/He .times. 129)F1 are so far the most susceptible to neonatal thymectomy, and the incidence in females (25%) is significantly higher than that in males (6%). Mice with thyroid lesions usually had circulating antibodies to mouse thyroid extract. Histologically, lymphocytes and plasma cells were the main cellular types of infiltrates, and lymphoid follicles were seen in some cases. Adenoma-like nodular hyperplasia of thyroid epithelium was observed in several thymectomized mice, with or without lymphoid infiltration. Lymphoid infiltrations were often observed in such organs as the ovary, the stomach and the coagulating gland of thymectomized mice. These characteristics are compared with those of Hashimoto''s thyroiditis and with those of its other animal models [e.g., spontaneous autoimmune thyroiditis in the chicken], and possible mechanisms which may be involved in the present disease are discussed.