Induced Lymphocytic Thyroiditis in Dogs: Effect of Intrathyroidal Injection of Thyroid Autoantibodies

Multifocal infiltrations of lymphocytes and macrophages were present in the thyroid glands of dogs 1 month after an intrathyroidal injection (0.5 ml) of canine serum containing thyroglobulin autoantibodies. The development of thyroiditis was associated with a gradual increase in the incorporation of tritiated thymidine by the peripheral blood mononuclear cells. There was no alteration in circulating thyroid hormone values or thyroglobulin autoantibody titer for 1 month. Control dogs given a similar volume of canine serum without thyroglobulin antibodies did not have an inflammatory reaction in the thyroid gland, and the phytomitogen responses of lymphocytes did not change, compared with base-line values. An intrathyroidal injection of canine thyroglobulin autoantibodies induced lesions similar to naturally occurring lymphocytic thyroiditis in dogs, indicating that thyroid autoantibodies have an important role in the pathogenesis of immune-mediated thyroiditis.