![]() ![]() ![]() Additionally, some T cells recognizing self-antigen with high affinity will express the transcription factor Foxp3 (forkhead box P3) and become natural regulatory T cells (nTregs). Deleterious immune responses against self-antigens are normally prevented by the process of negative selection or central tolerance, in which developing T and B cells in the thymus and bone marrow are eliminated from the repertoire. As a result, a large number of developing lymphocytes will have receptors that can react to self-antigens, as well as innocuous foreign antigens such as food and commensal bacteria. The local and systemic effects of these regulatory T cells prevent potentially dangerous hypersensitivity reactions to harmless antigens derived from the intestine and hence are crucial players in immune homeostasis.ĭuring lymphocyte differentiation, a virtually unlimited repertoire of B- and T-cell receptors is generated to recognize all kinds of different antigens. ![]() We propose a model of stepwise induction of oral tolerance in which specialized populations of mucosal dendritic cells and the unique microenvironment of draining mesenteric lymph nodes combine to generate regulatory T cells that undergo subsequent expansion in the small intestinal lamina propria. Here we discuss the anatomical basis of antigen uptake and recognition in oral tolerance and highlight possible mechanisms underlying the immunosuppression. An analogous but more local process also regulates responses to commensal bacteria in the large intestine and, together, mucosally induced tolerance appears to prevent intestinal disorders such as food allergy, celiac disease, and inflammatory bowel diseases. Oral tolerance is the state of local and systemic immune unresponsiveness that is induced by oral administration of innocuous antigen such as food proteins. ![]()
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