Macrophage-restricted Interleukin-10 receptor-, but not IL-10 deficiency causes severe spontaneous colitis

Interleukin-10 (IL-10) is a pleiotropic anti-inflammatory cytokine produced and sensed by most hematopoietic cells. Genome wide association studies and experimental animal models point at a central role of the IL-10 axis in Inflammatory Bowel Diseases. Here we investigated the importance of intestinal macrophage production of IL-10 and their IL-10 exposure, as well as the existence of an IL-10-based autocrine regulatory loop in the gut. Specifically, we generated mice harboring IL-10 or IL-10 receptor (IL-10Rα) mutations in intestinal lamina propria-resident chemokine receptor CX3CR1hi-expressingmacrophages. We found macrophage-derived IL-10 dispensable for gut homeostasis and maintenance of colonic T regulatory cells. In contrast, loss of IL-10 receptor expression impaired the critical conditioning of these monocyte-derived macrophages, but resulted in spontaneous development of severe colitis. Collectively, our results highlight IL-10 as a critical homeostatic macrophage-conditioning factor in the colon and define intestinal CX3CR1hi macrophages as a decisive factor that determines gut health or inflammation.