Update on mucosal immunoglobulin A in gastrointestinal disease.

Purpose Of Review: To review recent findings dealing with the involvement of mucosal immunoglobulin A (IgA) in the gut barrier function and various gastrointestinal diseases. New information will be discussed in the context of previous knowledge in this field.

Recent Findings: The epithelial barrier function seems to be central in many mucosal disorders because it is decisive for host-microbial interactions and penetration of soluble antigens into the lamina propria. Secretory IgA contributes to the barrier function and recent evidence strongly supports the notion that such antibodies are involved in immunological homeostasis.

Summary: Inflammatory bowel disease involves a break of tolerance to the commensal microbiota. Aberrations in the mucosal IgA system may, therefore, be part of the inflammatory bowel disease pathogenesis. In gluten-induced enteropathy, however, it has been suggested that a mucosal IgA response may promote the progression of celiac disease and dermatitis herpetiformis by enhancing the uptake of gluten peptides and inhibiting the enzyme activity of tissue transglutaminase. A mucosal IgA response may also promote gastritis by protecting Helicobacter pylori from complement attack. In food allergy, several facets of the epithelial barrier function may show deficiency, including secretory IgA.