title: A coated tube assay for the detection of blocking thyrotropin receptor autoantibodies.
abstract: We developed a coated tube assay to discriminate TSH-receptor-stimulating autoantibodies [thyroid-stimulating antibodies (TSAb)] from those autoantibodies blocking TSH binding without intrinsic activation [thyroid-blocking antibodies (TBAb)]. The wild-type TSH receptor in the TSH binding-inhibitory assay was exchanged for a chimeric receptor where a TSAb epitope (amino acids 8-165) was replaced by comparable LH-R residues. Binding of (125)I-labeled TSH to this chimera could be inhibited by sera containing TBAb up to 95%. Sera from 316 patients with Graves' disease and 17 with autoimmune thyroid disease were grouped according to their bioassay activity. At the decision threshold, the chimera A assay had a sensitivity of 78.0% for TBAb with a specificity of 90.2%. In detail, 19 of 22 (86.4%) TBAb sera and 15 of 23 (65.2%) TSAb/TBAb sera were positive but only 32 of 216 (14.0%) TSAb sera and 5 of 72 (6.9%) bioassay negative sera. There was a weak but significant positive correlation (r = 0.46) between the chimera assay and the bioassay for TBAb. This is the first report of a coated tube assay for the determination of TBAb employing an adaptation of the TSH binding-inhibitory format, which could be a useful alternative to the bioassay.
authors.affiliation: MiLo GmbH, B.R.A.H.M.S. AG, Biotechnology Center Hennigsdorf/Berlin, D-16761 Hennigsdorf, Germany.
authors.forename: Waldemar B
authors.initials: WB
authors.lastname: Minich
authors.forename: Cornelia
authors.initials: C
authors.lastname: Lenzner
authors.forename: Andreas
authors.initials: A
authors.lastname: Bergmann
authors.forename: Nils G
authors.initials: NG
authors.lastname: Morgenthaler
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000097:blood*; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D006111:Graves Disease / Q000276:immunology; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D018828:Immunoglobulins, Thyroid-Stimulating / Q000097:blood; D007457:Iodine Radioisotopes; D051381:Rats; D011974:Receptors, LH / Q000235:genetics; D011989:Receptors, Thyrotropin / Q000097:blood* / Q000235:genetics; D011993:Recombinant Fusion Proteins; D012680:Sensitivity and Specificity; D013972:Thyrotropin / Q000378:metabolism; D014162:Transfection
chemical_list: D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; D007457:Iodine Radioisotopes; D011974:Receptors, LH; D011989:Receptors, Thyrotropin; D011993:Recombinant Fusion Proteins; C094372:thyrotropin-binding inhibitory immunoglobulin; D013972:Thyrotropin