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Abstract
The exposure of the human body to microorganisms occurs mostly at the mucosal surface of the gastrointestinal tract in the form of food, infectious or toxic antigens.
The gut is protected by several non-specific mechanisms. Epithelial cells form an important physical barrier via their intercellular tight junctions and rapid turnover.
The acid pH of the stomach is a formidable chemical barrier to many organisms, also the gut relies upon natural and acquired immune system to protect the host against different antigens.