The Role of Mast Cells in Intestinal Immunophysiology

Immunophysiology of the gut is the study of the regulation/modulation of its function by immune cells and factors. Fluid secretion is a key function of the intestine which aids digestion by maintaining the lumenal contents in a liquid state, promoting mixing of nutrients with digestive enzymes which are then presented to the absorptive epithelial cells. Fluid secretion is also a host defence mechanism of mucosa that serves to wash away noxious material from the epithelial surface. In the gut, active transport of negatively charged Cl- ions into the lumen by epithelial cells has been clearly shown to be the driving force for fluid secretion, while positively charged ions such as Na+ follow in response to the electrical gradient. Cl- channels open in response to increased concentrations of intracellular second messengers such as cAMP and Ca2+, resulting in ion and fluid movement across the gut wall.1