Characterization of different types of experimental autoimmune thyroiditis in the Buffalo strain rat.

We have compared features of experimental thyroiditis in the Buffalo strain rat induced by neonatal thymectomy, immunization with rat thyroglobulin (Tg) and complete Freund's adjuvant, and subcutaneous administration of trypan blue or 3-methylcholanthrene. The disease produced by neonatal thymectomy resulted in significantly worse thyroiditis and higher antibody levels than the other models and shared other features in common with Hashimoto's thyroiditis. In particular TSH levels were elevated, Tg antibodies had a restricted subclass distribution, the thyroid was infiltrated by both B cells and T cells (comprising equal numbers of W3/25 and Ox8 positive cells) and thyroid follicular cells were Ia antigen-positive in some of the thymectomy group animals. In the other forms of thyroiditis, the thyroid infiltrate was mainly composed of macrophages or dendritic cells and B cells. Different pathogenic mechanisms are probably involved in these models; the disease produced by neonatal thymectomy shows the closest similarity to Hashimoto's thyroiditis.