Regulatory T cells but not T helper 17 cells are modulated in an animal model of Graves' hyperthyroidism.

Graves' disease (GD) involves auto-immunity against thyroid cell antigens, but the reasons for the induction of auto-immunity are uncertain. We wished to investigate the role of T helper 17 (Th17) and regulatory T cells (Treg) in a mouse model of Graves' hyperthyroidism. The model was generated by immunizing mice with adenovirus expressing the autoantigen thyroid-stimulating hormone receptor (Ad-TSHR289). The frequencies of splenic Th17 and Treg were determined by flow cytometry. The levels of interleukin-17(IL-17), forkhead box P3 (Foxp3), and orphan retinoic acid nuclear receptor (RORγt) mRNA were determined by real-time PCR. The number of CD4(+)CD25(+)Foxp3(+) T lymphocyte was significantly reduced in the Ad-TSHR289 group compared with the Ad-control (P < 0.05). mRNA level for Foxp3 was less abundant in Ad-TSHR289 group compared with Ad-control (P < 0.05). However, CD4(+)IL-17(+) T-cell subpopulation and expression of RORγt mRNA did not differ significantly between Ad-TSHR289 and Ad-control groups (P > 0.05). Nevertheless, in Ad-TSHR289 group, a profound increase in the Th17/Treg ratios was found. The present study demonstrates that Th17 is not involved in promoting Graves' hyperthyroidism, while Treg and the ratio of Th17/Treg might play a role in the pathogenesis of Graves' hyperthyroidism.