IL-6 helps the regulators rein in T_H2 cells

This study shows an unexpected role for interleukin-6 (IL-6) during infection with Heligmosomoides polygyrus. Mice deficient in IL-6 developed more potent T helper 2 (T_H2) cell responses to H. polygyrus and had increased resistance to chronic infection. IL-6 deficiency led to increased eosinophilia and higher levels of IgE, but did not affect type 2 innate lymphoid cells. T_H17 cell numbers were increased in H. polygyrus-infected IL-6-deficient mice, but their depletion had no effect on worm burdens. However, IL-6-deficient mice had an altered regulatory T (T_Reg) cell phenotype (characterized by lower expression of FOXP3, Helios and GATA3, and increased production of IL-2 and IL-17), and restoration of normal T_Reg cell function decreased the T_H2 cell response to H. polygyrus. This suggests that IL-6 stabilizes T_Reg cells during helminth infection.