Immunologic Diseases of the Gastrointestinal Tract

The gastrointestinal (GI) tract contains the largest mass of immune cells of any organ in the body. Despite continuous exposure to environmental and dietary antigens and to commensal microbes, pathogens, and their metabolic products, the gut is able to maintain epithelial barrier integrity and homeostatic immune regulation. However, the GI tract is susceptible to immune-mediated inflammation from pathogenic organisms, epithelial barrier dysfunction as well as autoimmunity and immunodeficiency. This chapter discusses the more frequent immunological diseases of the GI tract likely to be encountered in the clinic, including autoimmune gastritis, chronic Helicobacter pylori gastritis, celiac disease, inflammatory bowel diseases (IBDs; Crohn disease, ulcerative colitis, microscopic colitis, and eosinophilic esophagitis), and GI complications of primary immunodeficiency. The focus is on the clinical presentation, mechanisms of disease, and current diagnosis and treatment of these conditions.