Establishment of a novel assay for the quantification of antibodies to the insulin receptor. A, Detection principle by a bridge format; the fusion protein of insulin receptor with luciferase (1) is used as detector, the antibodies (Abs) serve as a bridge (2) between detector and the catcher antigen (3) that is a tagged insulin receptor immobilized to the support via a precoated tag-specific monoclonal Ab (mAb) (4). B, Dose-response curve of luciferase signals (RLU; relative light units) in response to increasing concentrations of Abs (unrelated SELENBP1-mAb1 as negative control, vs 2 InsR-specific mAb as positive controls) under the standardized test conditions for InsR-aAb.