Antibodies reactive with an intracellular epitope of a recombinant 64 kDa thyroid and eye muscle protein in patients with thyroid autoimmunity and ophthalmopathy

We have developed an enzyme-linked immunosorbent assay (ELISA) for the measurement of antibodies reactive with a 98 amino acid fragment, called D₁, of a recombinant thyroid and eye muscle membrane protein corresponding to a MW of 64 kDa (called ₁D) in the serum of patients with thyroid autoimmunity with and without ophthalmopathy. Antibodies against the D¹ fragment expressed as a fusion protein with β galactosidase, were detected in 29% of patients with thyroid-associated ophthalmopathy (TAO) of 3 yr duration, in 40% of patients with Graves’ hyperthyroidism (GH) without evident eye disease, in 31% of patients with lid lag and retraction but no other signs of progressive ophthalmopathy, in 25% of patients with euthyroid Graves’ disease and in 43% of patients with untreated Hashimoto’s thyroiditis (HT), but in none of 14 patients with other (non-immunological) thyroid disorders. Although tests were positive in 6 out of the 15 patients with ophthalmopathy and no overt thyroid autoimmunity overall there was no close association of the antibodies with clinical features of the eye disease or its course. In those sera in which Western blotting for antibodies reactive with a 64 kDa eye muscle membrane protein and ELISA were both carried out there was no close correlation between the two tests. In order to better understand the significance of antibodies reactive with 64 kDa eye muscle and thyroid membrane autoantigens and their possible relationship to ophthalmopathy it will be necessary to perform prospective studies of patients with untreated Graves’ hyperthyroidism beginning before the onset of eye signs, using antibody assays incorporating full length recombinant proteins.