T-cell restriction in thyroid eye disease

Infiltrating immunocompetent cells act to establish and perpetuate the orbital autoimmune process in thyroid eye disease (TED). Until recently, it has remained unclear whether T cells infiltrating the orbital connective/fatty tissue and extraocular muscles represent a primary immune response that is specifically directed against orbital antigens. In addition, despite a close clinical and temporal association of the thyroidal and extrathyroidal manifestations in Graves' disease (GD), it has not been proven whether T cells infiltrating thyroid, orbital, and pretibial tissue in patients with TED and pretibial dermopathy (PTD) are directed against certain antigenic determinants shared between these anatomically distinct tissues. Using polymerase chain reaction (PCR)-based molecular analysis of T-cell antigen receptor (TcR) variable (V) region genes, we have demonstrated marked restriction of orbital and pretibial TcR Valpha and Vbeta genes in patients with active TED and PTD. In addition, molecular analysis of T cells in paired samples of extraocular muscle and orbital connective/fatty tissue revealed usage of similar TcR V genes. In contrast, TcR V gene restriction was either absent or much less pronounced in patients with longstanding TED and PTD. Comparison of TcR V genes in T cells obtained from thyroid gland, orbital tissue, pretibial tissue, and peripheral blood of three individual patients with active GD, TED, and PTD also revealed marked restriction and, in addition, striking similarities of TcR V gene usage. Sequencing of complementarity determining regions 3 (CDR3) and junctional domains of TcR Vbeta genes confirmed oligoclonality of intrathyroidal, orbital, and pretibial T cells. Moreover, several conserved junctional motifs were shared by T cells infiltrating the thyroid gland and the extrathyroidal sites. Taken together, these data suggest that, in patients with GD and extrathyroidal manifestations, similar antigenic determinants may be responsible for recruitment and oligoclonal expansion of T cells both within the thyroid gland and in the involved extrathyroidal sites.