IL-33 mediated stromal-myeloid cell crosstalk controls intestinal helminth infestation

Abstract Interleukin-33 (IL-33) is a nuclear cytokine of the interleukin-1 family and is released upon cell damage thereby acting as an alarmin. IL-33 plays an essential role in promoting host-protective immune responses against helminth parasites at different mucosal surfaces including the intestine. However, early events after gastrointestinal nematode infection are poorly understood and the cellular source of IL-33 in the gut remains ill-defined. Here we show that Cxcl13-Cre-positive fibroblastic stromal cells (FSCs) of the lamina propria are the main source of IL-33 in the small intestine. Within the first days of nematode infection, lamina propria FSCs showed strongly increased IL-33 expression. Ablation of IL-33 in Cxcl-13-Cre-positive FSCs resulted in an increased infestation with the gastrointestinal nematode Heligmosomoides polygyrus bakeri. We found that myeloid cells were recruited to the site of worm invasion early after infection and that the upregulation of a distinct set of inflammatory cytokines was dependent on FSC-derived IL-33. Collectively, these data unveil that IL-33-mediated crosstalk between stromal and myeloid cells is a critical event during the initial immune response against gastrointestinal nematodes.