IL-4 together with IL-1β induces antitumor Th9 cell differentiation in the absence of TGF-β signaling

IL-9-producing CD4 + (Th9) cells are a subset of CD4 + T-helper cells that are endowed with powerful antitumor capacity. Both IL-4 and TGF-β have been reported to be indispensable for Th9 cell-priming and differentiation. Here we show, by contrast, that Th9 cell development can occur in the absence of TGF-β signaling. When TGF-β was replaced by IL-1β, the combination of IL-1β and IL-4 efficiently promoted IL-9-producing T cells (Th9 IL-4+IL-1β ). Th9 IL-4+ IL-1β cells are phenotypically distinct T cells compared to classic Th9 cells (Th9 IL-4+TGF-β ) and other Th cells, and are enriched for IL-1 and NF-κB gene signatures. Inhibition of NF-κB but not TGF-β-signaling negates IL-9 production by Th9 IL-4+IL-1β cells. Furthermore, when compared with classic Th9 IL-4+TGF-β cells, Th9 IL-4+IL-1β cells are less exhausted, exhibit cytotoxic T effector gene signature and tumor killing function, and exert a superior antitumor response in a mouse melanoma model. Our study thus describes an alternative pathway for Th9 cell differentiation and provides a potential avenue for antitumor therapies. CD4 + helper T cells producing IL-9 (Th9) have been implicated in anti-tumor immunity, with Th9 differentiation inducible in vitro via IL-4 and TGFβ treatment. Here the authors show that replacing TGFβ with IL-1β induces a distinct IL-9 + CD4 + population that have strong cytotoxic and anti-tumor activity in preclinical mouse models.