IL-10 from intestinal macrophages prevents excessive innate immune responses to bacteria by limiting IL-23 synthesis

Innate immune responses must be regulated in the intestine to prevent excessive inflammation. Here, using gene reporter mice, we show that a subset of mouse colonic macrophages constitutively produced the anti-inflammatory cytokine IL-10. In mice infected with Citrobacter rodentium, which is considered similar to enteropathogenic Escherichia coli infection in humans, macrophage IL-10 was required to prevent intestinal pathology and to promote survival. The synthesis of the proinflammatory cytokine IL-23 was significantly increased in infected mice with a myeloid cell specific deletion of IL-10 and the addition of IL-10 reduced in vitro IL-23 production by intestinal macrophages. Furthermore, blockade of IL-23 led to reduced morbidity and mortality in the context of macrophage IL-10 deficiency. Transcriptome analysis indicated that the reporter positive and negative colonic macrophage subsets were highly similar, but the reporter positive cells differed for the expression of CD163, an IL-10 target gene, suggesting an autocrine IL-10 signal, and when obtained from infected mice, they had reduced IL-23p19 mRNA. Interestingly, only transfer of the reporter positive cells could rescue IL-10 deficient infected mice. Therefore, these data indicate a pivotal role for a subset of intestinal macrophages that constitutively produces IL-10, perhaps acting in part in autocrine fashion, in controlling excessive innate immune activation, regulation of IL-23 production, and prevention of tissue damage after an acute bacterial infection in the intestine.

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Krause P, Morris V, Greenbaum JA, Park Y, Bjoerheden U, Mikulski Z, Muffley T, Shui JW, Kim G, Cheroutre H, Liu YC, Peters B, Kronenberg M, Murai M