[Shigella: from the rupture to the invasion and to the destruction of the colonic epithelium].

CROSSING THE EPITHELIAL BARRIER: Shigella acts on the immune system in order to cross the intestinal epithelial barrier which is normally impermeable to intestinal flora. Among the effectors of the immune system of the colonic mucosa are translocation sites corresponding to lymphatic follicles carrying a follicular epithelium in the presence of M cells. These cells capture molecules, particles and microorganisms from the intestinal barrier that they translocate to immune competent cells present in the follicles (antigen presenting cells including resident macrophages and then B and T lymphocytes). MACROPHAGE APTOTOSIS AND ITS CONSEQUENCES: The first cell infected by Shigella appears to be the macrophage once the translocation has been made via the M cells. This infection rapidly leads to apoptotic death of the macrophage allowing the Shigella to infect the laterobasal epithelial cells and the development of an inflammatory response. This response in turn facilitates the invasion, rupture and permeability of the intestinal epithelium and the initiation, by Shigella, of a cell-to-cell invasion pathway.