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M cells and the follicle-associated epithelium
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Hiroshi Ohno, Marian Neutra, Ifor R. Williams
The cardinal feature of the FAE is the presence of M cells. The major function of M cells is to deliver samples of macromolecules, particulate foreign material, and microorganisms by transepithelial transport from the lumen to organized mucosal lymphoid tissues. M cells, like all the epithelial cells of the gastrointestinal and respiratory tracts, are joined to adjacent epithelial cells by junctional proteins that seal the paracellular pathway. However, M cells provide functional openings through the epithelial barrier by their transepithelial vesicular transport activity. M cell differentiation is largely restricted to the FAE; consequently, transport of foreign material and microbes across the epithelial barrier is targeted to the organized, inductive sites of the mucosal immune system. M cells were first recognized microscopically by their unique morphology, especially their intraepithelial “pocket” that provides a sequestered space for activated or memory B and T lymphocytes and DCs. The pocket shortens the transcytotic pathway and provides for rapid delivery of luminal samples to intraepithelial and subepithelial cells.
Autologous Hematopoietic Stem Cell Transplantation for Crohn’s Disease
Published in Richard K. Burt, Alberto M. Marmont, Stem Cell Therapy for Autoimmune Disease, 2019
Robert M. Craig, Richard K. Burt
M cells are the first step in initiating a mucosal immune response or tolerance. Lumenal antigens are taken up by M cells and transported to intraepithelial lymphocytes and/or macrophages that have been invaginated or surrounded by the cytoplasm of M-cells. The origin of M-cells remains controversial and may be differentiated from crypt stem cells or represent a modified epithelial cell since ex vivo co-culture of lymphocytes from Peyer’s patches induces conversion of enterocytes into antigen transporting M cells.3,4 M cells do not present MHC class II antigens or co-stimulatory molecules. After uptake and transport by M-cells, antigens are processed and represented within Peyer’s patches by follicular dendritic and other antigen presenting cells.
Leukocytes and lymphoid tissues: The framework of the immune system
Published in Gabriel Virella, Medical Immunology, 2019
Peyer's patches are lymphoid structures disseminated through the submucosal space of the small intestine (Figure 2.8). The follicles of the intestinal Peyer's patches are extremely rich in B cells, which differentiate into IgA-producing plasma cells. Specialized epithelial cells, known as M cells, abound in the dome epithelia of Peyer's patches, particularly at the ileum. These cells take up small particles, virus, bacteria, etc., and deliver them to submucosal macrophages, where the engulfed material will be processed and presented to T and B lymphocytes.
From intestinal colonization to systemic infections: Candida albicans translocation and dissemination
Published in Gut Microbes, 2022
Jakob L. Sprague, Lydia Kasper, Bernhard Hube
The contributions of microfold (M) cells and Peyer’s patches of the intestine to translocation of bacterial pathogens during systemic infection has been well studied and reviewed.52 M cells are specialized intestinal epithelial cells for phagocytosis of material from the lumen and its presentation to resident phagocytes, like dendritic cells (Figure 1b).61 M cells are located within lymphoid tissues of the gut, like Peyer’s patches in the small intestine.61 Bacteria such as Shigella flexneri and S. typhimurium are known to specifically target M cells during infection. S. flexneri can also enter M cells, though not exclusively, and use these as a mechanism for translocation across the epithelium.62S. typhimurium exclusively invades M cells causing extensive host-cell death and is even able to enter adjacent epithelial cells.63S. typhimurium has also been shown to use phagocytic cells present at Peyer’s patches for transport into the bloodstream. The presence of dendritic cells in an in vitro model with intestinal epithelial cells facilitated transport across the barrier.64 The same study also showed the uptake of S. typhimurium from the intestine in an in vivo mouse model.
Issues currently complicating the risk assessment of synthetic amorphous silica (SAS) nanoparticles after oral exposure
Published in Nanotoxicology, 2021
Walter Brand, Petra C. E. van Kesteren, Ruud J. B. Peters, Agnes G. Oomen
Of all human tissues studied, the highest concentrations of total-Si were detected in human intestinal tissues (5.2–191mg/kg) (Table 3). Note that it cannot be excluded that a part of the Si reported in intestinal tissues could be present in the outer mucus layer, and is not absorbed in the intestinal cells (Frey et al. 2019). The two regions analyzed, ileum and jejunum, contain Peyer’s patches, a gut associated lymphoid tissue where M-cells are located. M-cells are held responsible for the uptake of particles in the gut, in addition to endocytosis of smaller particles by enterocytes throughout the intestine (Frey et al. 2019; Powell et al. 2010). As mentioned before, the total-Si ingested orally can partly originate from other sources than SAS, including from other Si-particles (silicates, e.g. E 552). It has to be noted that Powell et al. (1996) detected a relative large number of different silicate particles in the gut associated lymphoid tissue (Powell et al. 1996).
Development of SARS-CoV-2 vaccines: should we focus on mucosal immunity?
Published in Expert Opinion on Biological Therapy, 2020
Leticia Moreno-Fierros, Ileana García-Silva, Sergio Rosales-Mendoza
There is a myriad of alternatives to achieve a proper bioavailability and immunogenicity for mucosal vaccines; namely using refined vaccine formulations containing rationally-designed antigens, mucoadhesive excipients, and specific adjuvants [30]. The design of antigens optimized for mucosal immunogenicity is one of the key aspects to ensure vaccine efficacy. The use of well-known mucosal carriers with adjuvant activity such as the B subunit of the heat labile enterotoxin from E. coli is advisable [31]. Targeting M cell through the use of specific ligands, e.g. the Co-1 peptide, is also advisable [32]. Another possible innovation consists in developing vaccines based on low-cost oral delivery vehicles (e.g. plant cells, yeast, and Gram-positive bacteria), which could render low-cost mucosal vaccines with the added benefit of showing improved immunogenicity with respect to soluble antigens [33]. Moreover, the design of VLPs with improved mucosal immunogenicity can be also achieved by different approaches. For instance, decorating VLPs with variant specific surface proteins from Giardia lamblia has allowed to effectively induce, upon oral administration, immunoprotection against influenza and cancer in murine models [34].