Clec12a tempers inflammation while restricting expansion of a colitogenic commensal

Abstract

SUMMARYRegulation of the microbiota is critical to intestinal health yet the mechanisms employed by innate immunity remain unclear. Here we show that mice deficient in the C-Type-lectin receptor, Clec12a developed severe colitis, which was dependent on the microbiota. Fecal-microbiota-transplantation (FMT) studies into germfree mice revealed a colitogenic microbiota formed within Clec12a-/-mice that was marked by expansion of the gram-positive organism,Faecalibaculum rodentium. Treatment withF. rodentiumwas sufficient to worsen colitis in wild-type mice. Macrophages within the gut express the highest levels of Clec12a. Cytokine and sequencing analysis in Clec12a-/-macrophages revealed heighten inflammation but marked reduction in genes associated with phagocytosis. Indeed, Clec12a-/-macrophages are impaired in their ability to uptakeF. rodentium.Purified Clec12a had higher binding to gram-positive organisms such asF. rodentium. Thus, our data identifies Clec12a as an innate immune surveillance mechanism to control expansion of potentially harmful commensals without overt inflammation.