T Cells and the Autoimmune Response to the TSH Receptor

Production of IgG class TSH receptor (TSHR) autoantibodies, the direct cause of Graves’ disease, requires “help” from CD4+ T cells. However, there is a major difference in the way that T and B cells recognize antigen. Thus, TSHR autoantibodies, like antibodies to other protein antigens, interact predominantly with conformational epitopes on intact antigen (Chapter 4). In contrast, T cells only interact with antigen that has been internalized and degraded into peptides. Peptides (~ 20 amino acids) are presented to T cells within a groove in MHC class II molecules on the surface of the antigen-presenting cell (APC)(Fig.1).