Résumé
The development of T helper (T...)17 and regulatory T (T...) cells is reciprocally regulated by cytokines. Transforming growth factor (TGF)-β alone induces FoxP3... T... cells, but together with IL-6 or IL-21 induces T...17 cells. Here we demonstrate that IL-9 is a key molecule that affects differentiation of T...17 cells and T... function. IL-9 predominantly produced by T...17 cells, synergizes with TGF-β1 to differentiate naive CD4... T cells into T...17 cells, while IL-9 secretion by T...17 cells is regulated by IL-23. Interestingly, IL-9 enhances the suppressive functions of FoxP3... CD4... T... cells in vitro, and absence of IL-9 signaling weakens the suppressive activity of nT... in vivo, leading to an increase in effector cells and worsening of experimental autoimmune encephalomyelitis. The mechanism of IL-9 effects on T...17 and T... is through activation of STAT3 and STAT5 signaling. Our findings highlight a role of IL-9 as a regulator of pathogenic versus protective mechanisms of immune responses. (ProQuest: ... denotes formulae/symbols omitted.)