Immunologic Aspects of Hepatic and Gastrointestinal Tract Disease

THE IMMUNOLOGIC system appears to play an important role in maintaining the homeostasis of the gastrointestinal (GI) tract. Pathogenic immune reactions have been described in a variety of GI tract and liver diseases. Among the important structural and functional immunologic components of the GI tract are Peyer's patches, intraepithelial lymphocytes, diffusely distributed lamina propria plasmacytes, and all classes of immunoglobulin. In addition, nonimmune mechanisms are important in protecting the gut. These include the barrier to swallowed organisms created by gastric secretions, the cleansing effect on the intestines of peristalsis, and possibly of mucous secretion, the effect of indigenous bacterial flora on potential pathogens, and the filtering effect of the liver. Immunologic mechanisms characteristic of the mucosal immune system may have particular relevance to hypersensitivity reactions in the GI tract. First, mucosal lymphoid follicles (Peyer's patches) may be an important source of IgE cells. Thus, it has recently been shown that