In Vivo: Studies in mouse APCs (DCs and macrophages) identifie QS-21 as an activator of the NLRP3 inflammasome, and cause subsequent release of caspase-1 dependent proinflammatory cytokines I1-1β/I1-18 that can promote Th 17 cell maturation or drive INF-γ-mediated Th1 responses, respectively.