Induction of Graves-like disease in mice by immunization with fibroblasts transfected with the thyrotropin receptor and a class II molecule (1)
Numerous attempts to develop a Graves disease (GD) model by immunizing animals with the extracellular domain of the thyrotropin receptor (TSHR) have largely failed. In most cases, antibodies to the TSHR that could inhibit thyrotropin (TSH) binding and, in some cases, thyroiditis with a large lymphocytic infiltration were produced.
When a murine MHC class II-transfected fibroblast cell line, RT 4.15HP, or its classII -untransfected control counterpart, DAP.3, was transfected with human TSHR, both expressed the receptor in a functional array, exhibiting similar TSH-increased stimulation of the cAMP signal system.
Measurements of TBII activity showed that most mice immunized with hTSHR-transfected RT4.15HP cells developed serum TBII activity. Five of 24 mice in the experiment noted 1 also developed hyperthyroidism as evidenced by significantly elevated serum T4 levels.
Serum triiodothyronine levels were significantly increased in parallel with the increased T4 levels.
The thyroid glands of mice with high serum T4 showed marked hypertrophy and exhibited thyrocyte hypercellularity with intrusion into the follicular lumen.
Protein A-purified IgG from mice immunized with hTSHR-transfected RT4.15HP cells, who showed high serum thyroid hormone levels, had significant levels of thyroid-stimulating activity in cAMP assays, measured using CHO cells transfected with hTSHR. In contrast, IgG from mice immunized with hTSHR-transfected RT4.15HP cells, whose thyroid hormone levels were not elevated, exhibited no thyroid-stimulating activity.
H-2s and H-2q have been reported to be high-responder strains in terms of their levels of anti-TSHR antibodies when immunized with soluble human TSHR. This possibility would be consistent with the prevalence of certain HLA haplotypes (B35) in GD but not Hashimoto thyroiditis.