Superantigen-Induced Changes in Epithelial Ion Transport and Barrier Function: Use of an In Vitro Model

The small intestine selectively absorbs digested macromolecules, vitamins, minerals, and electrolytes, whereas the large intestine supports the majority of the gut microflora and reabsorbs water. These activities are the primary functions of the intestinal epithelium, a single layer of cells (principally transporting enterocytes, but also goblet cells, Paneth cells, enteroendocrine cells, and microfold “M” cells) that line the gut and interface directly with the contents of the lumen -effectively, the external environment. As such, the intestinal epithelium comprises a physical barrier that, in concert with nutrient absorption, must manage the transport of antigenic stimuli and prevent the incursion of potentially pathogenic organisms. The gut is continuously exposed to a high load of potentially noxious material derived from the diet and gut microflora, so it is not surprising that the intestine contains a large proportion of the body’s immune cells and is effectively the body’s largest immune organ.