Neuroimmune signaling in regulation of intestinal ion transport.

Complex interactions between the enteric nervous system, the immune system, and the epithelium govern the transport rates of salt and water across the intestinal lining. Luminal antigens or bacterial products are detected by the immune system, which triggers a cascade of events associated with the release of inflammatory mediators. These mediators, by lowering the response threshold for transmission in some neural circuits, augment ongoing neural reflexes that promote secretion. Associated with these effects is a dampening of responses in other neural circuits innervating the mucosal effectors. Selective excitation and inhibition of the neural reflex circuitry coupled with direct actions of inflammatory mediators on epithelial cells result in stereotypical motility and secretory patterns that are characterized by strong muscular contractions, copious secretion, and diarrhea.