Immunocompetent cells are present normally in the mucosa of the gut; t
heir numbers increase during inflammatory conditions. When activated,
these cells release potent chemical mediators or cytokines, which have
the ability to induce intestinal pathophysiologic disorders. Activati
on can occur in response to a variety of stimuli, including specific a
ntigens, noxious substances, or bacteria and their products. Neural in
volvement may amplify or inhibit the response. Exciting new evidence i
ndicates that epithelial cells participate in immune and inflammatory
reactions, This article reviews information reported in the past year
about functional changes in the intestinal mucosa in response to immun
e mediators or activation of immune or inflammatory cells.