Immunological aspects of inflammatory bowel diseases of the human gut.

The gut has a highly specialized immune apparatus, particularly involving the production of protective secretory immunoglobulin A (IgA), but also involving T-cell immunity. Secretory IgA plays a major role in preventing antigen uptake, both of infectious and non-infectious types. IgA immune responses are initiated by antigen uptake into specialized lymphoid aggregates such as Peyer's patches, and IgA plasma cell precursors are subsequently distributed throughout the gut and also over other mucosal surfaces. The clinical consequences of perturbation of the local immune system of the gut are surveyed in this article, including the consequences of immunodeficiency and the conditions reflecting an enhanced expression of immunity in the gut mucosa. The potential impact of non-steroidal anti-inflammatory drugs on the local immune system is discussed.