Dietary antigens limit mucosal immunity by inducing regulatory T cells in the small intestine

Abstract

Dietary antigens are normally rendered non-immunogenic through a poorly understood “oral tolerance” mechanism that involves immunosuppressive regulatory T (Treg) cells, especially Treg cells induced from conventional T cells in the periphery (pTregs). While orally introducing nominal protein antigens induces such pTreg cells, whether a typical diet induces a population of pTreg cells under normal conditions is unknown. By using germ-free mice raised and bred on an elemental diet devoid of dietary antigens, we demonstrate that the vast majority of the small intestinal pTreg cells under normal conditions is induced by dietary antigens from solid foods. Moreover, these pTreg cells have a limited lifespan, are distinguishable from microbiota-induced pTreg cells, and repress underlying strong immunity to ingested protein antigens.