Intestinal mucosal epithelium: the barrier to sepsis

The intestinal epithelium provides a critical barrier to pathogens and their toxins within the intestinal lumen. The epithelium is capable of directly interacting with intestinal pathogens such as Salmonella species, resulting in a release of cytokines beneath the epithelium that likely play a role in sepsis. More directly, the epithelium expresses Toll-like receptors so that it can directly respond to luminal lipopolysaccharide. Breaching of the epithelial barrier is likely the principal cause of sepsis in patients with compromised intestinal circulation. However, a number of reparative mechanisms have developed to rapidly repair epithelial defects, including epithelial migration (restitution) and closure of injured tight junctions. Therefore, barrier function and prevention of sepsis are related to the ability of the epithelium to react in an appropriate manner to luminal bacteria, prevent passage of bacteria across the barrier, and rapidly repair the barrier when it is damaged.