title: A novel bioassay for anti-thyrotrophin receptor autoantibodies detects both thyroid-blocking and stimulating activity.
abstract: Autoantibodies to the thyrotrophin (TSH) receptor (anti-TSHR) are unique, in that they are involved directly in the pathophysiology of certain autoimmune thyroid diseases (AITD). Thyroid-stimulating antibodies (TSAb) act as agonists that activate the thyroid gland and cause Graves' disease. Other anti-TSHR antibodies block TSH and can cause hypothyroidism. Thyroid-blocking antibodies (TBAb) have not been studied as extensively as TSAb. We developed a TBAb bioassay based on a cell line that expresses a chimeric TSHR. The 50% inhibitory concentration of the chimeric Chinese hamster ovary (CHO)-Luc cells was more than five-fold lower compared with the wild-type CHO-Luc cells. We tested the performance of this bioassay using a thyroid-blocking monoclonal antibody K1-70, established an assay cut-off and detected TBAb in 15 of 50 (30%) patients with AITD. Interestingly, the assay detects both TSAb and TBAb and measures the net activity of a mixture of both types of antibodies. There was a high correlation (R(2) 0·9, P < 0·0001) between the results of the TSAb assay and the negative percentage inhibition of the TBAb assay. The TBAb bioassay was approximately 20-fold more sensitive than a commercially available TSHR binding assay (TRAb). In contrast to TRAb, sera with high levels of TBAb activity were able to be diluted several hundred-fold and still exhibit blocking activity above the cut-off level. Thus, this TBAb bioassay provides a useful tool for measuring the activity of anti-TSHR antibodies and may help clinicians to characterize the diverse clinical presentations of patients with AITD.
authors: Diagnostic Hybrids Inc., Athens, Ohio, USA.
authors: Y
authors: Y
authors: Li
authors: J
authors: J
authors: Kim
authors: T
authors: T
authors: Diana
authors: R
authors: R
authors: Klasen
authors: P D
authors: PD
authors: Olivo
authors: G J
authors: GJ
authors: Kahaly
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D001327:Autoimmune Diseases / Q000175:diagnosis / Q000276:immunology; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D018828:Immunoglobulins, Thyroid-Stimulating / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D011989:Receptors, Thyrotropin / Q000819:agonists / Q000037:antagonists & inhibitors / Q000276:immunology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013959:Thyroid Diseases / Q000175:diagnosis / Q000276:immunology; D013972:Thyrotropin / Q000494:pharmacology
chemical_list: D019138:Antibodies, Blocking; D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin; D013972:Thyrotropin
keywords: autoimmune thyroid disease; bioassay; thyroid-blocking antibody; thyrotrophin receptor autoantibody
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