Identification and characterization of dietary antigens in oral tolerance

Food antigens elicit immune tolerance through the action of intestinal regulatory T (Treg) cells. Unlike food allergens, the proteins that mediate tolerance are mostly undescribed. Here, we found that epitopes derived from seed storage proteins are targets of murine intestinal Treg cells, with the most frequent response targeting the C terminus of the maize protein alpha-zein. A major histocompatibility complex (MHC) tetramer loaded with this antigen revealed that zein-specific T cells are predominantly intestinal Treg cells, develop concurrently with weaning, and constitute up to 2% of the peripheral Treg cell pool. Zein-responsive Treg cells repressed naïve T cell proliferation ex vivo, and prior dietary exposure resulted in a constrained response upon diverse inflammatory challenges in vivo, supporting a specific role for gut-resident Treg cells in suppressing systemic immune responses. Our work reveals the development, immune-suppressive characteristics, and function of naturally occurring Treg cells that recognize dietary seed storage proteins, a previously undescribed class of antigens in oral tolerance.