The specificity of autoantibodies in Graves' ophthalmopathy.

An autoantibody to orbital antigens is found in patients with Graves' ophthalmopathy. This autoantibody also binds to skeletal muscle antigen. Occasional positive responses have been seen in patients with Hashimoto's disease and with non-organ-specific autoimmune disease. Eye muscle has a higher innervation ratio than skeletal muscle and may be of different embryological origin, but it is nevertheless closely related to skeletal muscle and it is perhaps not surprising that the antibody should interact with both these types of muscle. What remains quite unexplained, is why the disease process apparently affects eye muscle only. The antigen appears to be distinct from thyroidal antigens, but further work with a larger patient population is necessary before one can be certain of this. To date it has been possible to exclude the cytoskeletal proteins, myosin and actin, and also the TSH receptor as possible candidates for the responsible antigens. Further studies are in progress to elucidate the nature of this muscle antigen.