The presence of autoantibodies directed to thyroid plasma membrane antigens in sera of patients with thyroid disorders, estimated by the reaction with labelled protein A

Abstract

The presence of antithyroid plasma membrane antibodies (ATMA) was detected in 97% of patients with untreated hyperthyroid Graves'' disease, 85% of methimazole-treated hyperthyroid Graves'' disease, 25% of Hashimoto''s thyrodiditis and 6.9% of patients with toxic nodular goiter. The ATMA index was negative in all healthy blood donors, in patients with non-toxic nodular goiter, with the thyrocardiac syndrome and with simple obesity. Studies of patients with non-thyroid autoimmune diseases revealed that ATMA is positive in 11% of patients with scleroderma, 17.6% of systemic lupus erythematosus and 16% of rheumatoid arthritis. The amount of Ig bound to thyroid plasma membranes after pre-incubation with serum from patients with Graves'' disease varied from 4.2-25.2 pmol/mg of membrane protein; these values are several times higher than the maximal binding capacity for TSA which is 1.28 pmol/mg protein. In the majority of the cases studied TSH did not significantly inhibit IgG bound from thyroid plasma membranes. Significant amounts of IgG were displaced by an excess of TSH only in 3 cases with untreated hyperthyroid Graves'' disease.