Abstract

Healthy people are constantly exposed to foreign proteins but in contrast to allergic individuals they do not develop any immune response. Cornerstone of such difference is tolerance. Oral tolerance in allergic people is of highest priority. Oral tolerance is specific suppression of cellular and/or humoral immune responses to an antigen by prior administration of the antigen by the oral route. It may develop naturally or be allergen immunotherapy (AIT) induced. Mechanisms of natural tolerance development are not fully understood. Current data was mainly obtained from studies in patients, who receive AIT or have been exposed to high doses of allergens. Still it is not clear, why some allergic patients develop natural tolerance and some do not. Oral tolerance is characterized by depletion or suppression of antigen-specific T-cells and induction of Treg-cells, which are clue cells in depression of inflammatory response to good antigens. Oral tolerance to harmless dietary antigens develops due to different factors including antigen composition and dose, routes of antigen entry at sensibilization, regulatory T cells (Treg-cells) induction. Breastfeeding is also involved in tolerance development. Physical barriers, digestion, opportunistic pathogenic intestinal bacteria, gut-associated lymphoid tissue (GALT) immune cells, and immune regulation are supposed to be involved in oral tolerance development in the gastrointestinal tract. In the present paper key factors and mechanisms involved in oral tolerance development as well as in food allergy development suppression are described. Full understanding of oral tolerance mechanisms will help to reduce food allergy prevalence rates through preexposure prophylaxis (due to natural tolerance development) as well as to create new strategies of food allergy therapy (due to induced tolerance).

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