Mucosal immunity.

Food allergy is the manifestation of an abnormal immune response to antigen delivered by the oral route. Normal mucosal immune responses are generally associated with suppression of immunity. A normal mucosal immune response relies heavily on a number of factors: strong physical barriers, luminal digestion of potential antigens, selective antigen sampling sites, and unique T-cell subpopulations that effect suppression. In the newborn, several of these pathways are not matured, allowing for sensitization rather than suppression. With age, the mucosa associated lymphoid tissue matures, and in most individuals this allows for generation of the normal suppressed tone of the mucosa associated lymphoid tissue. As a consequence, food allergies are largely outgrown. This article deals with the normal facets of mucosal immune responses and postulates how the different processes may be defective in food-allergic patients.