Tryptophan feeding of the IDO1-AhR axis in host-microbial symbiosis

Abstract

The large variety of microbial species in the human microbiome plays an important role in human health by affecting tissue differentiation, modulation of the immune system, as well as the general response against infectious pathogens. The aryl hydrocarbon receptor (AhR) contributes to immune homeostasis as having an antimicrobial role on the one hand - owing to AhR-dependent IL-22 transcription - and, on the other, an anti-inflammatory role in that it mediates the differentiation of regulatory T cells (Tregs). Here, we have examined the multifaceted physiological role of AhR as resulting from the vast array of recently described AhR ligands and of the multiplicity of AhR-expressing cells in host-microbial symbiosis in mammals.