Role of M Cells in Intestinal Barrier Function

Abstract

M cells are known as specialized epithelial cells of the follicle‐associated epithelium of the gastrointestinal tract. As M cells have a high capacity for transcytosis of a wide range of microorganisms and macromolecules, they are believed to act as an antigen sampling system. The primary physiological role of M cells seems to be the rapid uptake and presentation of particular antigens and microorganisms to the immune cells of the lymphoid follicle to induce an effective immune response. In contrast to absorptive enterocytes, M cells do not exert direct defense mechanisms to antigens and pathogens in the gut lumen. Therefore, they provide functional openings of the epithelial barrier. Although M cells represent a weak point of the epithelial barrier, even under noninflamed conditions, there seems to be a balance between antigen uptake and immunological response. The low number of M cells in the gastrointestinal tract and the direct contact to immune cells in the lamina propria usually prevent the occurrence of mucosal inflammation. During chronic intestinal inflammation we observe an increase of M cell number and apoptosis selectively in M cells. M cell damage seems to be responsible for the increase of the uptake of microorganisms that is observed during intestinal inflammation. Under inflammatory conditions in the intestine, the maintenance of the epithelial barrier is broken and M cells seem to play a major role during this process.

Functional RNA Delivery Targeted to Dendritic Cells By Synthetic Nanoparticles

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Persorption Mechanisms of Luminal Antigenic Particulates via Apoptotic Epithelial Cells of Intestinal Villi into Systemic Blood Circulation in Orally Immunized Rats

“…In general, the intestinal barrier is permeable to low-molecular-weight nutrients, such as amino acids, small peptides, monosaccharides, fatty acids and glycerol, but impermeable to macromolecules, particular antigens and most microorganisms [25]. Information on luminal antigens and microorganisms is generally taken up by special epithelial cells, M cells, exclusively located in the follicle-associated epithelium of mucosal lymphatic tissues [25].…”

Manning the Barricades: Role of the Gut Epithelium in Crohn’s Disease

“…Various models of chemically induced intestinal inflammation have been used to study M cells, the FAE and interplay with the underlying Peyer's patches. In an indomethacin-induced enteritis model in rats, M cell numbers increased initially and showed increased apoptosis in inflamed tissue only (Kucharzik et al, 2000;Lugering et al, 2004). In the DSS-induced model of colitis in mice, increased severity of disease was associated with lack of both Peyer's patches and lymph nodes, but not with mice lacking Peyer's patches only (Spahn et al, 2002).…”