Reflections on Thyroid Autoimmunity: A Personal Overview from the Past into the Future

Abstract

After investigating thyroid autoimmunity for more than 40 years, we present a personal perspective on the field. Despite effective therapies for Graves' hyperthyroidism and Hashimoto's thyroiditis, cures are elusive. Novel forms of therapy are being developed, such as small molecule inhibitors of the TSH receptor (TSHR), but cure will require immunotherapy. This goal requires advances in understanding the pathogenesis of thyroid autoimmunity, the 'keys' for which are the thyroid antigens themselves. Presently, however, greater investigative focus is on non-thyroid specific immune cell types and molecules. Thyroid autoantigens are the drivers of the autoimmune response, a prime example being the TSHR. In our view, the TSHR is the culprit as well as the victim in Graves' disease because of its unique structure. Unlike the closely related gonadotropin receptors, the TSHR cleaves into subunits and there is strong evidence that its shed extracellular A-subunit, not the holoreceptor, is the major antigen driving pathogenic thyroid stimulating autoantibodies (TSAb) development. There is no Graves' disease of the gonads. Studies of potential antigen-specific immunotherapies require an animal model. Such models have been developed in which TSAb can be induced or, more importantly, arise spontaneously. Not appreciated until recently by thyroid investigators is that B cell surface autoantibodies are highly efficient 'antigen receptors' and the epitope to which an autoantibody binds influences antigen processing and which peptide is presented to T cells. These animal models and recombinant human autoantibodies cloned from Graves' and Hashimoto's B cells (plasma cells) are available for study by future generations.