Tuft cell IL-17RB restrains IL-25 bioavailability and reveals context-dependent ILC2 hypoproliferation

Abstract

The tuft cell–group 2 innate lymphoid cell (ILC2) circuit orchestrates rapid type 2 responses upon detecting microbially derived succinate and luminal helminths. Our findings delineate key mechanistic steps involving IP3R2 engagement and Ca2+ flux, governing interleukin-25 (IL-25) production by tuft cells triggered by succinate detection. While IL-17RB has a pivotal intrinsic role in ILC2 activation, it exerts a regulatory function in tuft cells. Tuft cells exhibit constitutive Il25 expression, placing them in an anticipatory state that facilitates rapid production of IL-25 protein for ILC2 activation. Tuft cell IL-17RB is crucial for restraining IL-25 bioavailability, preventing excessive tonic ILC2 stimulation due to basal Il25 expression. Supraoptimal ILC2 stimulation by IL-25 resulting from tuft cell Il17rb deficiency or prolonged succinate exposure induces a state of hypoproliferation in ILC2s, also observed in chronic helminth infection. Our study offers critical insights into the regulatory dynamics of IL-25 in this circuit, highlighting the delicate tuning required for responses to diverse luminal states. Tuft cells constitutively express IL-25 to sustain ILC2 homeostasis in the intestine, but mechanisms driving IL-25 secretion have been unclear. Here, Feng et al. find that tuft cells express IL-17RB, which is required to regulate the bioavailability of IL-25 and to restrain the activation of ILC2s during homeostasis.