The Roles and Mechanisms of Gut Microbiota in Food Allergy

Figure 2

Commensal bacteria mediate immune tolerance. The gut microbiota modulates oral tolerance to food antigens through multiple mechanisms. First, gut microbiota promotes the differentiation of Treg cells. Microbial signals increase the levels of IL-10, TGF-β, and RA, which leads to the expansion of Treg cells. Macrophage-derived IL-1β promotes IL-2 and GM-CSF release from ILC3s, which are essential for induction of Treg cells. Microbial metabolites are also involved in shaping the differentiation of Tregs, including SCFAs, tryptophan metabolites, and bile acid. Second, gut microbiota reduces circulating basophil populations. Third, gut microbiota promotes epithelial barrier integrity. Microbial signals induce IL-22 production and Th17 differentiation, which in turn modulate mucous, mucin, and occludin, thereby strengthening the epithelial barrier. IL-10: interleukin-10; TGF-β: transforming growth factor-β; RA: retinoic acid; ILC3: type 3 innate lymphoid cells; SCFAs: short-chain fatty acids; Th17: T helper 17; TJ: tight junction.