Elevated thyroglobulin level is associated with dysfunction of regulatory T cells in patients with thyroid nodules

OBJECTIVE: Thyroid nodules are usually accompanied by elevated thyroglobulin (Tg) level and autoimmune thyroid diseases (AITDs). However, the relationship between Tg and AITDs is not fully understood. Dysfunction of regulatory T cells (Tregs) plays an important role in the development of AITDs. We aimed to evaluate the effects of Tg on the function of Tregs in patients with thyroid nodules. METHODS: Tg levels and the functions of Tregs in peripheral blood and thyroid tissues of patients with thyroid nodules from Nanjing First Hospital were evaluated. The effects of Tg on the function of Tregs from healthy donors were also assessed in vitro. The function of Tregs was defined as an inhibitory effect of Tregs on the effector T cell (CD4(+) CD25(−) T cell) proliferation rate. RESULTS: The level of Tg in peripheral blood correlated negatively with the inhibitory function of Tregs (R = 0.398, P = 0.03), and Tregs function declined significantly in the high Tg group (Tg >77 μg/L) compared with the normal Tg group (11.4 ± 3.9% vs 27.5 ± 3.5%, P < 0.05). Compared with peripheral blood, the function of Tregs in thyroid declined significantly (P < 0.01), but the proportion of FOXP3(+) Tregs in thyroid increased (P < 0.01). High concentration of Tg (100 μg/mL) inhibited the function of Tregs and downregulated FOXP3, TGF-β and IL-10 mRNA expression in Tregs in vitro. CONCLUSIONS: Elevated Tg level could impair the function of Tregs, which might increase the risk of AITDs in patient with thyroid nodules.