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Category: Clinical Microbiology
Role of Intestinal M Cells in Microbial Pathogenesis, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817848/9781555812614_Chap02-1.gif /docserver/preview/fulltext/10.1128/9781555817848/9781555812614_Chap02-2.gifAbstract:
The intestinal epithelium is remarkable in its ability to serve multiple functions simultaneously. Mucosal lymphoid follicles with associated follicle-associated epithelium (FAE) are widely distributed in the digestive tract. The Peyer's patches have been most extensively studied because they consist of large aggregates of follicles visible on the antimesenteric surface of the intestine. The ability of pathogens to exploit the M-cell transport pathway is indeed impressive when one considers the rarity of these cells in the epithelium. M cells can engulf noninvasive microorganisms including Vibrio cholerae by actin-dependent phagocytosis, while certain pathogens such as Salmonella spp. disrupt the M-cell apical cytoskeletal organization and induce macropinocytosis. Information about the events immediately following M-cell transport is scarce. Although pathogens can exploit subepithelial antigen-presenting cells and use the migration of these cells to reach local and distant targets, in most cases M-cell-mediated uptake of microorganisms probably results in immune responses that are beneficial to the host. The ability of poliovirus to use the M-cell pathway for penetration of the epithelial barrier is now being exploited as an oral vaccine strategy. A clearer understanding of adherence mechanisms will facilitate the design of mucosal vaccines that are targeted to organized mucosal lymphoid tissues for efficient induction of protective immune responses.
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Interactions of bacteria and viruses with M cells. The schematic drawings in panels A, B, and D depict the apical pole of an M cell and the brush borders of adjacent enterocytes in the FAE. A portion of the M-cell intraepithelial pocket with lymphocytes and part of a phagocytic cell (Φ) are shown. (C) An entire M cell along with associated cells within the pocket and under the epithelium. (A) V. cholerae and enteropathogenic E. coli (EPEC) are noninvasive pathogens that colonize enterocyte surfaces but also adhere to M cells. V. cholerae is endocytosed and transported to the pocket, but EPEC induces formation of attaching and effacing lesions on the M-cell surface. (B) S. enterica serovars Typhi and Typhimurium adhere preferentially (but not exclusively) to M cells. They invade the Peyer's patch by inducing ruffling of the M-cell apical surface and macropinocytosis. (C) Shigella flexneri is efficiently transported by M cells. Once on the basolateral side of the epithelium, S. flexneri invades both epithelial and subepithelial cells, which in turn release cytokines and chemokines that recruit polymorphonuclear leukocytes (PMNs). (D) Reovirus adheres selectively to M cells in mice. HIV can adhere to the surface of the FAE in experimental animals. M-cell adherence results in transcytosis of virus into the M-cell pocket. (Reproduced with permission from reference 114 .)
Interactions of bacteria and viruses with M cells. The schematic drawings in panels A, B, and D depict the apical pole of an M cell and the brush borders of adjacent enterocytes in the FAE. A portion of the M-cell intraepithelial pocket with lymphocytes and part of a phagocytic cell (Φ) are shown. (C) An entire M cell along with associated cells within the pocket and under the epithelium. (A) V. cholerae and enteropathogenic E. coli (EPEC) are noninvasive pathogens that colonize enterocyte surfaces but also adhere to M cells. V. cholerae is endocytosed and transported to the pocket, but EPEC induces formation of attaching and effacing lesions on the M-cell surface. (B) S. enterica serovars Typhi and Typhimurium adhere preferentially (but not exclusively) to M cells. They invade the Peyer's patch by inducing ruffling of the M-cell apical surface and macropinocytosis. (C) Shigella flexneri is efficiently transported by M cells. Once on the basolateral side of the epithelium, S. flexneri invades both epithelial and subepithelial cells, which in turn release cytokines and chemokines that recruit polymorphonuclear leukocytes (PMNs). (D) Reovirus adheres selectively to M cells in mice. HIV can adhere to the surface of the FAE in experimental animals. M-cell adherence results in transcytosis of virus into the M-cell pocket. (Reproduced with permission from reference 114 .)