TSH RECEPTOR TRANSCRIPTS AND TSH RECEPTOR-LIKE IMMUNOREACTIVITY IN ORBITAL AND PRETIBIAL FIBROBLASTS OF PATIENTS WITH GRAVES OPHTHALMOPATHYAND PRETIBIAL MYXEDEMA

Several lines of experimental and clinical evidence favor a close etio logic link between Graves' disease and its associated extrathyroidal m anifestations, ophthalmopathy and pretibial dermopathy. The human TSHR represents a candidate antigen shared between the thyroid gland and t he involved extrathyroidal sites in Graves' disease. Here, we demonstr ate that ribonucleic acid encoding exons 1-10 of human TSHR can be det ected in fibroblasts derived from the affected orbital and pretibial s pace in patients with Graves' ophthalmopathy and pretibial dermopathy. RNA prepared from cultured fibroblasts was reverse transcribed and th e resulting cDNA amplified by the polymerase chain reaction using prim ers spanning exons 1 through 10 of TSHR. The predicted transcripts (18 90 and 2092 bp, respectively) were obtained with cDNA derived from orb ital and pretibial fibroblasts of all patients with GO and PTM, and or bital fibroblasts of one healthy individual, and confirmed by southern hybridization. Sequencing of TSHR transcripts confirmed their identit y with the reported nucleotide sequence of the human TSHR. Immunostain ing using both monoclonal and polyclonal antibodies directed against t he recombinant human TSHR revealed specific TSHR-like immunoreactivity in fibroblasts and adipose/connective tissue derived from the orbital and pretibial space of patients with GO and PTD, but not in normal in dividuals or control tissues. Detection, within the orbital and pretib ial tissues, of RNA encoding nonvariant hT-SHR and of immunoreactivity for this important autoantigen in Graves' disease suggests that the p athogenic role of the TSHR may extend beyond the thyroid gland, and ma y include the associated extrathyroidal manifestations.