The lack of specificity of ophthalmic immunoglobulins in Graves' disease.

Immunoglobulins (Igs) binding to retro-orbital muscle (ROM) antigens, known as ophthalmic Igs (OIg), were measured using a 100,000 X g sediment of porcine ROM as antigen in a solid phase [125I]protein A binding assay. Serum samples from 50 control subjects bound from 0.60-2.42 times the amount of [125I]protein A as did the normal reference serum samples, defined as the OIg ratio. Serum from 95 patients with hyperthyroid Graves' disease had OIg ratios from 0.64-9.99, with 24 (25%) being positive [OIg ratio greater than 2.05 (mean + 2 SD of the normal group)]. Ten patients with euthyroid Graves' ophthalmopathy had OIg ratios from 1.01-6.33, with 6 (60%) being positive. Among those Graves' disease patients with ophthalmopathy (n = 19) and the euthyroid Graves' ophthalmopathy patients there was a good correlation between the severity of eye signs and the OIg ratio. The OIg-positive serum samples cross-reacted with skeletal muscle and thyroid as well as with ROM antigen. This lack of specificity contradicts previous reports, but does not rule out a role for these antibodies in the etiology of Graves' ophthalmopathy.