ANALYSIS OF AUTOANTIBODY REACTIVITY IN PATIENTS WITH GRAVES-DISEASE USING RECOMBINANT EXTRACELLULAR DOMAIN OF THE HUMAN THYROTROPIN RECEPTOR AND SYNTHETIC PEPTIDES

Graves' disease is characterized by hyperthyroidism leading to enhance d production of thyroid hormones. Hyperthyroidism is primarily mediate d by the binding of autoantibodies to the thyrotropin receptor (TSHr). In the past, either thyroid cells or thyroid membranes were used as a source of TSHr to detect anti-TSHr antibodies. Recently, we expressed the extracellular domain of the human TSHr (ETSHr) using the baculovi rus expression system. In this study, we used ETSHr protein in an ELIS A to detect anti-TSHr antibodies. Our data show that this assay can be used to analyze and quantitate isotype specific antibodies against th e TSHr. To map immunogenic epitopes on the TSHr, we tested patients se ra against synthetic peptides derived from two highly immunogenic regi ons (amino acid, AA 12-46 and 316-397) of the receptor. Although sera from patients with Graves' disease reacted with several peptides, they showed particularly strong reactivity against peptides from a relativ ely narrow region (i.e. AA 352-394) of the TSHr. The present study dem onstrates the usefulness of the recombinant ETSHr to detect and charac terize anti-TSHr antibodies in a simple and sensitive ELISA, and has l ead to the identification of some of the immunoreactive epitopes on th e TSHr.