Human orbital tissue and thyroid membranes express a 64 kDa protein which is recognized by autoantibodies in the serum of patients with thyroid-associated ophthalmopathy.

A 64 kDa protein has been identified in the membrane fraction of human eye muscle, orbital connective tissue and thyroid, by testing sera of patients with thyroid-associated ophthalmopathy in SDS-polyacrylamide gel electrophoresis and Western blotting. Antibodies to this membrane antigen seem characteristic of the early stage of ophthalmopathy. In the thyroid this newly recognized protein seems different from previously known membrane antigens. A thyroid antibody reactive with a 64 kDa membrane antigen in eye muscle could explain the very frequent association of ophthalmopathy with autoimmune thyroid disease.