Intestinal mucosal immune defense mechanisms.

The intestinal mucosal immune defense mechanisms involve both humoral and cellular immunity. The prominence of suppressor/cytotoxic T lymphocytes in the epithelial layer suggests that these interepithelial lymphocytes play a role in defense against infections within this layer. Secretory IgA is overwhelmingly the major humoral immune response along the gastrointestinal tract and along other mucosal surfaces (respiratory tract, mammary glands, salivary glands, and lacrimal glands). While the functions of secretory IgA are incompletely understood, it is clear that it prevents attachment of microorganisms and toxins (cholera toxin, shiga toxin, etc.) to the surface epithelial cells. Furthermore, secretory IgA may collaborate with eosinophils or killer lymphocytes to mediate cytotoxic reactions against enteropathogens. By learning more about the mucosal immune response, we should be able to understand the relationship between the lamina propria plasmacytosis in inflammatory bowel disease and the increased number of interepithelial lymphocytes that we see in gluten-sensitive enteropathy and the underlying pathogenic mechanisms.