Prevalence and significance of antibodies reactive with eye muscle membrane antigens in sera from patients with Graves' ophthalmopathy and other thyroid and nonthyroid diseases

We have investigated the antibody responses made to porcine eye muscle antigens by sera from patients with Graves' disease and ophthalmopathy (GO) on Western blotting in a retrospective cross sectional study. Reactivity to several different eye muscle antigens was observed; however, antibodies to two antigens of 64 and 95 kd were found predominantly in sera with a prevalence of 63.6% (14/22) and 50.0% (11/22), respectively. In Graves' patients without GO the levels dropped to 18.2% (6/33) and 9.1% (3/33), and to 10.0% (2/20) and 20.0% (4/20) in patients with other thyroid diseases, and 0% (0/29) and 20.7% (6/29) in patients with nonthyroid diseases. Healthy control subjects gave positive responses in 8.0% (2/25) and 12.0% (3/25) of sera tested against the two antigens. The prevalence of the responses in patients with GO was significantly different when compared with normals and other patient groups (p < 0.05 and p < 0.01). All patients with ophthalmopathy graded class 3 or 4 and most of the patients with GO and a suppressed thyrotropin (TSH) value at the time of investigation reacted with one or other of the two antigens. Similar prevalences of response were found to the 64 and 95 antigens in those patients with GO whether they were thyrotropin receptor antibodies (TSHR-Ab) positive or negative (p > 0.05). However, the prevalence of the response to the 64 kd antigen in the TSHR-Ab positive group of patients without GO (31.3%) was significantly higher than that found in the TSHR-Ab negative (5.9%, p < 0.05) group. 81.8% (9/11) of patients with GO and a suppressed TSH recognized the 64 kd antigen compared with 45.5% with a normal TSH value (p < 0.05) and 16.7% without GO and a normal TSH (p < 0.01). In additional studies we have shown that a mouse monoclonal antibody (3B12) raised to the extracellular domain of the human TSH receptor also reacted with a 55 kd antigen in pig eye muscle but was not inhibited from its binding to either pig eye antigen or human TSH receptor antigen (3A1) by any of our patients' sera. These data suggest that serum antibodies reactive with porcine eye muscle antigens are potentially useful markers of ophthalmopathy in Graves' patients and should be further evaluated in longitudinal studies to see if they can predict the onset or regression of Graves' ophthalmopathy.