Food allergy: Immunophysiology

The gastrointestinal tract forms a barrier to the outside environment while providing a surface area to process and absorb ingested food and to discharge waste products. The immune system associated with this barrier, the gut-associated lymphoid tissue (GALT), is capable of discriminating between dangerous pathogens and harmless foreign proteins and commensal organisms. Although intact food antigens penetrate the gastrointestinal tract, they generally do not cause clinical symptoms because most individuals develop tolerance. In mucosal tissues, soluble antigens, such as food antigens, are typically poor immunogens and induce a state of unresponsiveness known as oral tolerance. T lymphocytes are largely responsible for the development of allergic disease through their release of cytokines that regulate multiple aspects of the allergic phenotype. T cells may contribute to the development of allergic disease by means of an overabundance of proallergic cytokines or a lack of regulatory cytokines. It is likely that both of these aspects are involved in the development of allergic sensitization to food proteins.