Pathogen-induced human T _H17 cells produce IFN-γ or IL-10 and are regulated by IL-1β

IL-17-producing CD4 ⁺ T helper cells (T ^H17) have been extensively investigated in mouse models of autoimmunity ¹. However, the requirements for differentiation and the properties of pathogen-induced human T ^H17 cells remain poorly defined. Using an approach that combines the in vitro priming of naive T cells with the ex vivo analysis of memory T cells, we describe here two types of human T ^H17 cells with distinct effector function and differentiation requirements. Candida albicans-specific T ^H17 cells produced IL-17 and IFN-γ, but no IL-10, whereas Staphylococcus aureus-specific T ^H17 cells produced IL-17 and could produce IL-10 upon restimulation. IL-6, IL-23 and IL-1β contributed to T ^H17 differentiation induced by both pathogens, but IL-1β was essential in C. albicans-induced T ^H17 differentiation to counteract the inhibitory activity of IL-12 and to prime IL-17/IFN-γ double-producing cells. In addition, IL-1β inhibited IL-10 production in differentiating and in memory T ^H17 cells, whereas blockade of IL-1β in vivo led to increased IL-10 production by memory T ^H17 cells. We also show that, after restimulation, T ^H17 cells transiently downregulated IL-17 production through a mechanism that involved IL-2-induced activation of STAT5 and decreased expression of ROR-γt. Taken together these findings demonstrate that by eliciting different cytokines C. albicans and S. aureus prime T ^H17 cells that produce either IFN-γ or IL-10, and identify IL-1β and IL-2 as pro-and anti-inflammatory regulators of T ^H17 cells both at priming and in the effector phase.