Perspectives in mucosal immunity: a ruminant model.

All mammalian species have developed specialized defence mechanisms at the interface between mucosal surfaces and the environment and this system operates independently of the systemic immune system. Attachment of organisms to the mucosal epithelium is a primary prerequisite for infection and is an important virulence determinant for pathogens of these sites. The mucosal immune defences are thus characterized by production of IgA antibodies, the principal mode of action of which is to inhibit the adherence of pathogens to the mucosal epithelium. This introduction to the symposium on mucosal immunity will attempt to underline the role of local immunity in the intestine in providing local defence at that site, in addition to providing cellular molecular effectors for other mucosal sites.