The mucosa-associated lymphoid tissue structure, function, and derangements

Nearly 50% of the immune cells in the body lie just beneath the moist mucosal surfaces at intestinal and extra-intestinal sites. The study of this mucosal immune system in response to shock and to route and type of nutrition provides a cogent explanation for the reduced incidence of pneumonia with enteral feeding. Changes in immune cell mass and function are associated with deterioration of previously established immunity at mucosal surfaces, especially the respiratory tract. By understanding the mechanisms involved in this breakdown, therapeutic strategies can be developed to reduce septic complications in critical illness.