Fig. 5

Effects of AhR on colonization resistance against intestinal pathogens. Several immune mechanisms work in concert with the intestinal microbiota and contribute to colonization resistance against intestinal pathogens. AhR activation enhances the production of IL-1β by antigen presenting cells (APCs), which promotes neutrophil recruitment and pathogen eradication. AhR, in association with IL-23, is essential for the function of innate lymphoid cells (ILCs) and Th17/Th22 cells that control both commensals and pathogens through IL-22 production, inducing the production of antimicrobial peptides (AMPs) by intestinal epithelial cells. AMPs are also involved in colonization resistance against pathogens by shaping the microbiota that is then able to compete with pathogens for nutrients and regulate the secretion of intestinal IgA and IgG by B cells, contributing to pathogen eradication