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Autoimmune thyroid disease in man is commonly associated with autoantibodies against thyroglobulin, microsomes, and the TSH receptor, and the character and specificity of these antithyroid antibodies have been extensively utilized in investigating these conditions. In the present study we have asked whether other thyroid-related antigens exist, against which autoantibodies may be directed. A crude thyroid extract was separated by polyacrylamide gel electrophoresis followed by immunoblotting with serum obtained from patients with Graves' disease or Hashimoto's thyroiditis. Antibodies in sera from patients with Graves' disease and Hashimoto's thyroiditis reacted with many antigenic determinants in immunoblots of the thyroid membrane preparation (2000g supernatant). These determinants were disease specific in that sera from normals and patients with Addison's disease and rheumatoid arthritis did not react, but there was no difference between the patterns of reactivity with Graves' disease or Hashimoto's thyroiditis sera. Thyroglobulin produced two predominant bands of reactivity at 320 and 200 kDa, whereas purified microsomal antigen produced a triplet of bands around 105 kDa, when these preparations were reacted with appropriate autoimmune sera. Nonetheless, some sera produced additional bands with the microsomal antigen blots, indicating that some of the antigens which were detected using crude thyroid membrane remained in the microsome preparation to produce multiple antibody binding reactivities. We were unable to inhibit any of the antibody binding with TSH. Purification of individual thyroid antigens on the basis of their molecular weights should standardize current antibody assays and permit more detailed evaluation of the cellular immune responses in Graves' disease and Hashimoto's thyroiditis.

Autoimmune sera from patients with systemic lupus erythematosus, scleroderma, or both disorders reactive with the (U1)RNP and Sm antigens were analyzed according to their IgG- and IgM-autoantibody profiles by immunoblotting with HeLa nuclear extracts. Anti-(U1)RNP-specific autoantibodies directed against the 68-kDa polypeptide were found to be predominantly of the IgG type, whereas for the other (U1)RNP-specific protein, 33 kDa, a concomitant occurrence of IgG and IgM class autoantibodies was observed for most patients. In contrast, Sm-specific anti-29/28-kDa autoantibodies were found to be more frequently of the IgM than of the IgG type, while Sm-specific anti-16-kDa antibodies of both classes were present simultaneously in most sera. Of the serum collection reported here only one (U1)RNP-specific serum has been found which lacks anti-Sm antibodies of either class. In general, preclassification of sera by immunodiffusion and counterimmunoelectrophoresis corresponds to the IgG but not to the IgM profile as determined by immunoblotting.