Thyrotropin receptor antisera for the detection of immunoreactive protein species in retroocular fibroblasts obtained from patients with Graves’ ophthalmopathy

Autoimmunity against the TSH receptor (hTSH-R) is known to be the proximate cause of thyroidal activation in Graves' disease, but has not been definitively linked to extrathyroidal manifestations of this disorder, such as ophthalmopathy and pretibial myxedema. In an effort to increase our knowledge concerning mechanisms responsible for Graves' ophthalmopathy, we used antiserum directed against a highly immunogenic portion of the hTSH-R (amino acids 352-367; P1) to assess the presence of this receptor or immunologically related protein in cultured human retroocular fibroblasts obtained from patients with Graves' ophthalmopathy. Immunoenzymatic and immunofluorescent studies revealed specific staining of both cytoplasmic and cell membrane-associated protein in discrete vesicles. To further evaluate the immunoreactive species present in these cells, immunoblotting experiments were performed using hTSH-R-specific antisera (anti-P1) and sera obtained from patients with Graves' disease. Several protein bands were identified using both anti-P1 and Graves' disease patient sera, including species at mol wt of 95, 71, and 18 kilodaltons, the possible significance of which is discussed. The results support the hypothesis that immunity against the hTSH-R or related proteins contributes to the ophthalmopathy of Graves' disease.