Intestinal epithelial function: the case for immunophysiological regulation. Implications for disease (2).

Substantial amounts of data have been reported showing a role for immunomodulation of epithelial function (particularly ion secretion and permeability) using animal models of anaphylactic reactions. In part one of this review we outlined the main immune cell types and mediators/cytokines that are currently known to influence epithelial physiology either directly, or indirectly via an intermediate cell type. Here we will expand on the significance of these studies and show how antigenic activation of the mucosal immune system can evoke changes in epithelial function that may be beneficial to the host by mediating loss/inactivation of the antigen. However, a continued and inappropriate immune stimulation can lead to pathophysiological reactions and disease. Thus, we will present data on immune regulation of epithelial function with direct applicability to understanding the mechanism underlying human intestinal inflammatory and secretory disease. Finally, we highlight key strategic points in the cascade of immune events that can control epithelial function and thus may be of relevance in the formulation of new therapeutic approaches to intestinal inflammation.