Dietary Fiber and Bacterial SCFA Enhance Oral Tolerance and Protect against Food Allergy through Diverse Cellular Pathways

Abstract

The incidence of food allergies in western countries has increased dramatically in recent decades. Tolerance to food antigens relies on mucosal CD103(+) dendritic cells (DCs), which promote differentiation of regulatory T (Treg) cells. We show that high-fiber feeding in mice improved oral tolerance and protected from food allergy. High-fiber feeding reshaped gut microbial ecology and increased the release of short-chain fatty acids (SCFAs), particularly acetate and butyrate. High-fiber feeding enhanced oral tolerance and protected against food allergy by enhancing retinal dehydrogenase activity in CD103(+) DC. This protection depended on vitamin A in the diet. This feeding regimen also boosted IgA production and enhanced T follicular helper and mucosal germinal center responses. Mice lacking GPR43 or GPR109A, receptors for SCFAs, showed exacerbated food allergy and fewer CD103(+) DCs. Dietary elements, including fiber and vitamin A, therefore regulate numerous protective pathways in the gastrointestinal tract, necessary for immune non-responsiveness to food antigens.

Regulation of humoral immunity by gut microbial products

“…24 In low SCFA conditions due to low DF consumption, serum antibody and mucosal IgA levels are significantly decreased. 23,25 Germinal center responses in PPs are suppressed in low SCFA conditions but SCFA administration restored antibody production in mice fed a DF-free diet (Fig. 1).…”

“…26 Additionally, the roles of Retinaldehyde Dehydrogenase 2 (RALDH2)-expressing mucosal DCs in inducing IgA responses have been suggested. 25,27 Interestingly, it is not just intestinal IgA but also systemic IgG responses that are supported by SCFAs. 23 We will discuss the roles of non-B cells in mediating the regulatory effects of the gut microbiota on B cells responses in the next section.…”

“…RA is produced mainly in the small intestine, whereas SCFAs are mainly produced in the colon. 25,27 Therefore, this pathway is likely to be effective mainly in MLN which drains metabolites from both small and large intestines rather than in effector sites of the intestines where SCFAs and RA are produced in different locations.…”

The Evaluation of Some Dietary Fiber Rich by-Products in Ice Creams Made from the Traditional Pudding - Kesme Muhallebi

“…These anaerobic bacteria in the colon ferment fiber, into shortchain fatty acids. The fatty acids bind receptors known as "immune system cells" (Tan et al, 2016). In addition to © 2016 Conscientia Beam.…”

Allergy Immunity Regulation and Synergism of Bifidobacteria

“…High-fiber feeding also increased tolerogenic CD103 + DCs activity, leading to increased Treg cell differentiation [78].…”