Direct immunostaining of TSH receptor related autoantibodies in Graves' disease

Ten thyroid specimens from patients with Graves' disease were investigated immunohistologically with respect to the localisation of thyrotropin (TSH) receptor related autoantibodies. After conventional preparation of formalin-fixed and paraffin-embedded thyroid slices for immunostaining, 3-5 micron tissue sections were incubated with a porcine thyrotropin receptor containing membrane preparation (pTSH-R). The TSH receptor containing membrane fragments bound to the thyroid tissue were revealed with a slightly modified unlabelled PAP technique according to Sternberger, using an antiserum to pTSH-R obtained from immunized rabbits. This technique resulted in a staining of a considerable portion of plasma cells within the lymphoplasmacellular infiltrates of all the Graves thyroids. No staining occurred if for negative control either pTSH-R or its antiserum from rabbit was omitted. In addition, the staining reaction was markedly reduced by pretreatment of pTSH-R with serum from patients with Graves' disease in order to occupy its binding sites for autoantibodies prior to the staining procedure. It is concluded that the staining of the intrathyroidal plasma cells is due to their synthesis of autoantibodies directed against TSH receptor related structures of thyroid epithelia. The results are in keeping with the concept that the thyroid as the target organ itself is the site of autoantibody synthesis in Graves' disease.