HUMAN-IMMUNOGLOBULIN-G AUTOANTIBODIES TO THE THYROTROPIN RECEPTOR FROM EPSTEIN-BARR VIRUS-TRANSFORMED B-LYMPHOCYTES - CHARACTERIZATION BY IMMUNOPRECIPITATION WITH RECOMBINANT ANTIGEN AND BIOLOGICAL-ACTIVITY

The TSH receptor (TSH-R) is the target antigen for disease-related aut oantibodies in Graves' disease and primary myxoedema, but the repertoi re of the antibodies or the nature of the precise antigenic epitopes i s not known. We have immortalized peripheral blood B cells from six di fferent autoimmune thyroid disease patients with Epstein-Barr virus an d selected IgG-producing B cells by magnetic selection on anti-IgG-coa ted beads. Purified recombinant insect cell-derived extracellular regi on of TSH-R was used to identify the positive wells for expansion in c ulture. Stable B cell lines (n = 11) were obtained, which after limiti ng dilution led to two stable B cell clones. B cell lines and clones s ecreted IgG antibody that were shown to react biochemically with metab olically labeled or in vitro translated, nascent extracellular region of TSH-R, giving strong confirmatory evidence of the presence of anti- TSH-R antibody. Supernatants from lines contained thyroid-stimulating activity, thyroid-blocking activity (as assessed by inhibition of TSH- mediated cAMP stimulation), or both of these activities. Interestingly , antibodies with stimulating activity were generated from a primary m yxoedema patient, and antibodies of blocking specificities were obtain ed from newly diagnosed thyrotoxic Graves' disease patients. Our resul ts favor a fine balance between stimulating and blocking autoantibody activities in determining the clinical presentation observed in patien ts with autoimmune thyroid disease patients who have these antibodies present in their serum.