Concept, pathogenesis and autoimmune mechanisms of autoimmune TSH receptor disease.

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We studied the concept, pathogenesis and autoimmune mechanisms of autoimmune TSH receptor disease.1.A new concept of autoimmune TSH receptor diseasePreviously we have reported a highly significant difference in the HLA-DPw2 frequencies between Graves'disease and Hashimoto thyroiditis. In this study, we found genetic similarity of hypothyroidism due to blockig receptor antibody to Graves'disease but not to idiopathic myxedema. Further, strong and aberrant expressions of HLA-DP antigen on the thyroid epithelial cells of Graves'patients were also indicated. From these results, we proposed a new concept of autoimmune TSH receptor disease which is different from Hashimoto or idiopathic myxedema genetically and in the autoantibody producing mechanisms.2.PathogenesisPresence of certain heterogeneity in the T-and B-cell epitopes on the TSH receptor was observed. However, we demonstrated the primary importance of a TSH receptor specific region (around Aa No.355) on the receptor antibody product … More ion. A deletion mutant cDNA of the region was known to induce constitutive activation by transfection study, and further, we could produce stimulatory and blocking monoclonal receptor antibodies by immunizing a synthetic peptide corresponding to the region.3.Analysis of immunoglobulin gene of the receptor antibodiesThrough B-cell cloning from peripheral blood of the patients, we demonstrated that TSAb and TBII in Graves'sera are the products of different B-cells and that all TBII in hypothyroid patients sera are associated with TSBAb. We further analyzed immunoglobulin genes in details and performed to reconstitute VH and VK such obtained by transfection into mouse myeloma cell line. Thus, we were able to produce a recominant TSAb, in vitro.4.ConclusionAutoimmune TSH receptor disease was indicated to relate significantly with HLA-DP which may activate specific T cells via aberrant and strong expressions on the thyroid cells. Further, the initial step of the TSH receptor antibody production was considered to be originated from the sensitization of the TSH receptor specific region around Aa No.355. This was suggested to be followed by determinant spreading which would induce the productions of bioactive receptor antibodies such as TSAb and TSBAb. Less