Immunophysiology of the gut

Immunocompetent cells are present normally in the mucosa of the gut, and their numbers increase during inflammatory conditions. When activated, these cells release chemical mediators or cytokines that have the ability to alter intestinal function. Activation can occur in response to a variety of stimuli, ranging from specific antigens in sensitized hosts to molecules ingested or produced by bacteria or other pathogens. This article reviews information reported during the past year that describes functional changes of the gastrointestinal tract produced in response to immune activation or to inflammatory mediators. Studies of gastric acid secretion and ulcer formation are not included since they are covered separately in this issue.