Intestinal mucosal barrier

Its role in protecting the mucosal tissues and circulatory system from exposure to pro-inflammatory molecules, such as microorganisms, toxins, and antigens is vital for the maintenance of health and well-being.

The secretion of various molecules into the lumen reinforces the barrier function on the extra-epithelial side, while a variety of immune cells provide additional protection below the epithelial layer.

Crucial for forming an effective barrier is the precise control of the paracellular pathway (a route for translocation of molecules between cells).

[1] In addition to its protective function, the intestinal epithelium controls the selective uptake of beneficial ions, nutrients, and other substances from the lumen into the body.

[3][10] Antimicrobial peptides (AMPs), which are a diverse array of molecules that kill bacteria and fungi, are secreted by Paneth cells into the lumen.

[6] This population provides immune protection that is characterised by the rapid detection and killing of microorganisms that penetrate the intestinal epithelium.

[14] A disrupted intestinal mucosal barrier can allow passage of microbes, microbial products, and foreign antigens into the mucosa and the body proper.

[7] Defects in intestinal mucosal barrier function with the accompanying translocation of microbes and their products have been linked with a variety of conditions,[3] some of which are thought to additionally require a genetic predisposition.

[4] Intestinal barrier dysfunction may be a critical factor for antigen sensitisations and the IgE/mast cell-mediated anaphylactic effector phase of food allergies.

Nevertheless, there is a growing body of evidence that implicates increased intestinal permeability as a primary etiologic factor of inflammatory bowel disease pathogenesis.

By allowing gliadin, the causative agent of celiac disease, to cross the intestinal barrier, inappropriate activation of the immune system can occur.

[4] A combination of genetics, dysregulated intestinal barrier function, and inappropriate immune responses has been hypothesised to play a role in type 1 diabetes.

[4] Cummings adopted the term mucosal barrier in 2004 to describe the "complex structure that separates the internal milieu from the luminal environment.