Abstract
Group 2 innate lymphocytes (ILC2s) are prevalent in small intestine but their role during homeostasis is unclear. Here we show that thymic stromal lymphopoietin (TSLP)-a cytokine implicated in ILC2 activation-is expressed constitutively in subepithelial fibroblasts, including telocytes and crypt-associated trophocytes, which are specialized fibroblasts necessary to sustain epithelial identity. Feeding increases TSLP and induces ILC2 type 2 cytokines that are attenuated by deletion of TSLP in fibroblasts or TSLP receptor on ILC2s. Both mouse and human intestinal fibroblasts express receptors for glucagon-like peptide-2 (GLP-2)-an intestinotrophic growth factor released by enteroendocrine cells following food intake. GLP-2 promotes intestinal TSLP in mouse and human intestinal fibroblasts, and TSLP-dependent ILC2 activation and tuft cell hyperplasia in mice, thus linking nutrient detection with ILC2-mediated amplification of the tuft cell chemosensory circuit that promotes epithelial surveillance of ingested cargo.