Mucosal Immunity of the Intestine

Homeostasis and Inflammation

The intestinal epithelium is a front-line barrier that prevents potentially harmful organisms from gaining access to the host. It is covered on its apical (luminal) face with a mucous layer and anti-microbial peptides. At its basolateral surface is the lamina propria, which contains a range of immune cells that maintain homeostasis or respond to a breakdown of epithelial protection.

During homeostasis, immune system function in the lamina propria
permits the survival of commensal gut microorganisms. A multitude of lymphoid cell types in the lamina propria secrete immunoregulatory cytokines and other mediators that block the development of inflammatory responses, reinforce epithelial barrier integrity, and support the tolerogenic environment. 

During inflammation, normal epithelial barrier function is overwhelmed and pathogenic organisms can invade the epithelium. The lamina propria is then characterized by the infiltration of inflammatory cells and the production of inflammatory mediators. Phagocytic leukocytes remove infectious materials but cause tissue damage in the process. Chronic inflammation develops if the immune system cannot re-establish homeostasis.

Download this poster from R&D Systems for a detailed overview of the complex and intricate mechanisms underlying mucosal homeostasis and inflammation!