Increased expression of membrane-bound TGF-β1, GITR, and GITR ligand in patients with autoimmune thyroid disease

Regulatory T (Treg) cells, which play an important role in maintaining self-tolerance, are present in the thyroid-infiltrating lymphocytes of patients with autoimmune thyroid disease (AITD). We examined the expression of membrane-bound transforming growth factor-β1 (mTGF-β1), which mediates regulatory function and glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR). The protein in turn may inhibit regulatory function on Treg cells and TGF-β1 receptor II (TGF-βRII) and GITR expression. We also evaluated GITR ligand (GITRL) localization in thyroid tissues. mTGF-β1⁺ cells proportion in Treg cells was higher in the thyroid of patients with AITD than in their peripheral blood. GITR⁺ cells proportion among Tregs and Teff cells was also higher in the thyroid than in peripheral blood. GITRL expression in thyrocytes was higher in AITD patients than in healthy subjects. The interaction and balance of mTGF-β1, GITR, TGF-βRII, and GITRL especially thyrocyte GITRL expression, could be critical in AITD pathogenesis.