TSH binding site structures in human eye muscle fractions identified by using covalent-crosslinking

Immunohistochemical characterization of monoclonal antibodies directed against the TSH receptor

Monoclonal antibodies have been obtained by fusing mouse myeloma cells with spleen cells of mice immunized with crude thyroid membranes. Among the antibodies reactive with different thyroid antigenic components, three were found to specifically react with TSH receptor molecules. These antibodies displayed characteristic staining patterns on frozen sections of thyroid tissue from patients with various thyroid diseases upon identification of antibody binding by indirect peroxidase staining. No specific reactivity was detected with tissue from other human organs, such as pancreas, liver, fat, and muscle. The results demonstrate that the immunoperoxidase technique and the specificity of the monoclonal antibodies produced permitted the identification of cellular constituents that might be important antigens in autoimmune thyroid disease.

TSH receptor gene expression in retroocular fibroblasts

RNA was isolated from fibroblasts from the retroocular area, from endomysial fibroblasts obtained from orbital lateral rectus muscle, and from abdominal skin fibroblasts. The RNA was reverse transcribed into cDNA which was then used as a template for PCR with primers encompassing a portion (nucleotides 989-1235) of the extra-cellular domain of the human TSH receptor (hTSH-R). A definite 247 BP product was detected from fibroblast RNA by ethidium bromide staining, and was confirmed by hybridization with labelled hTSH-R cDNA. The product had homology with the known TSH-R cDNA. These studies indicate that human fibroblasts can express hTSH-R, and they suggest that a cross reactive immunologic response between anti-hTSH-R and these fibroblast TSH receptors may play a role in the genesis of Graves' ophthalmopathy.

Detection of TSH receptor RNA in cultured fibroblasts from patients with Graves' ophthalmopathy and pretibial dermopathy

Fibroblasts are target cells for the autoimmune process in Graves' ophthalmopathy and pretibial dermopathy. Because the autoantigen involved in the hyperthyroidism of Graves' disease is the TSH receptor, we sought to determine whether RNA encoding this receptor might be present in retroocular and pretibial fibroblasts. RNA was reverse transcribed and the resulting cDNA was amplified by the polymerase chain reaction using primers spanning a region of the extracellular domain of the human TSH receptor. The predicted amplified product, verified by direct sequencing, was detected when RNA was derived from fibroblasts, but not from the nonfibroblast cells studied. The demonstration in fibroblasts of RNA encoding this important autoantigen in Graves' disease suggests that the TSH receptor might play a role in the pathogenesis of the connective tissue manifestations of this disease.

Thyrotropin receptor autoantibodies recognizing two different epitopes on the TSH receptor: lack of relationship to patient age, sex, and ophthalmopathy

The existence of two populations of stimulatory TSH receptor autoantibodies against different epitopes raises the possibility of a link between one type of autoantibody and the clinical manifestations of Graves' disease. To test this hypothesis, serum immunoglobulins from 48 patients with Graves' disease were assayed for TSH binding inhibition (TBI) activity with two different recombinant TSH receptor variants (TSH-LHR-6 and TSH-LHR-6-A1) expressed on Chinese hamster ovary cells. The activity of 27 of the 48 patients' immunoglobulin samples was significantly less (difference in TBI value of 9% or greater) with chimera 6-A1 than with chimera 6. No immunoglobulin sample had significantly greater TSH binding inhibitory activity with chimera 6-A1 than with chimera 6. Sensitivity to the 6-A1 epitope substitution did not correlate with patient age, sex, or the presence or absence of hyperthyroidism. Further, there was no segregation of individual patients with TSH receptor autoantibodies with 6-A1 epitope sensitivity in terms of the past or present occurrence of ophthalmopathy, including the severity (total eye score), clinical activity, duration, and type of therapy. These data indicate that recognition by autoantibodies of the 6-A1 epitope on the TSH receptor is not associated with the ophthalmopathy of Graves' disease. However, the possibility cannot be excluded that other functional (or even nonfunctional receptor autoantibodies that are not detectable by present assays) may still play a role in the pathogenesis of Graves' ophthalmopathy.