GENETIC IMMUNIZATION AGAINST THE HUMAN THYROTROPIN RECEPTOR CAUSES THYROIDITIS AND ALLOWS PRODUCTION OF MONOCLONAL-ANTIBODIES RECOGNIZING THE NATIVE RECEPTOR

The generation of abs recognizing the native structure of the human th yrotropin receptor (hTSHR) has been difficult because there is current ly no method allowing the purification of correctly folded Ag in the a mounts required by classical immunization protocols, The majority of A bs made against the hTSHR react preferentially with denatured molecule s, We report that a humoral response against the native hTSHR, compati ble with mAb production, is elicited in mice by immunization Kith a DN A construct encoding the receptor, BALB/c mice were inoculated in the anterior tibialis muscle with 100 mu g of plasmid DNA harboring the hT SNR cDNA. Eleven weeks after the first injection, 10 mice of 14 showed by FACS analysis a strong IpG response against the hTSHR expressed at the surface of Chinese hamster ovary cells, A clear TSH-binding inhib iting Ig and thyrotropin-blocking Ab activity (competition with TSH bi nding and TSH activity, respectively) was demonstrated in the majority of sera tested. One serum exhibited a clear stimulating activity. Des pite the maintenance of normal circulating free T4 levels in all mice, these bioactivities persisted until 18 wk, in which mice were sacrifi ced, their thyroids were examined histologically, and spleens from two animals were used for mAb production, All mice displayed a severe lym phocytic infiltration of their thyroids, composed mostly of activated B cells. Three mAbs were produced against conformational epitopes of t he hTSHR, We conclude that genetic immunization is an efficient method of generating Abs recognizing the native structure of the hTSHR and a new way of inducing thyroiditis in mice murine.