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Biotechnology: Tuning Nanoscale Bio-systems
Published in Paula V. Messina, Luciano A. Benedini, Damián Placente, Tomorrow’s Healthcare by Nano-sized Approaches, 2020
Paula V. Messina, Luciano A. Benedini, Damián Placente
Although they are not the most popular, they have also been employed for the attainment of oral plant-based vaccines. Once these vaccines pass through the gastric environment and reach the small intestine, antigens are incorporated into the specialized epithelial cells of the mucosa-associated lymphoid tissues (M cells) for the induction of mucosal and systemic immune responses (Takeyama et al. 2015). The delivery of recombinant vaccines in edible plant organs is an outstanding goal because it would be advantageous to use locally grown plants for vaccination campaigns (Fischer et al. 2004). Several vaccines have been expressed in transgenic potatoes, tomato and banana including the hepatitis B surface antigen and the heat labile enterotoxin B subunit (LTB) of Escherichia coli. Vectors derived from tobacco mosaic virus have been used to produce oral antihypertensive peptide (angiotensin-1-converting enzyme inhibitor) in tomato (Giddings et al. 2000) and rabies G protein has been expressed in several species, including tomato, spinach and carrot (Rojas-Anaya et al. 2009).
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.
Immune Responses
Published in Ronald Fayer, Lihua Xiao, Cryptosporidium and Cryptosporidiosis, 2007
Adaptive immune responses in the intestine may be initiated in the Peyer’s patches (PPs). Within the epithelium overlying mucosal lymphoid follicles are specialized epithelial cells called M cells that transport particulate antigens from the gut lumen into the lymphoid tissue where they undergo phagocytosis by dendritic cells and can be presented to T-cells. Ultrastructural studies have shown Cryptosporidium entering guinea-pig PP via M cells and the parasites were also observed within phagocytic cells underlying the epithelium (Marcial and Madara, 1986). Also, during C. parvum infection of mice, a 10-fold increase in numbers of certain T-cell subsets and B cells within PP has been reported (Mariotte et al., 2004). These findings imply that the PPs are key sites for initiating adaptive immune responses.
Microplastics and human health: Integrating pharmacokinetics
Published in Critical Reviews in Environmental Science and Technology, 2023
The main routes of exposure to microplastics for humans consist of ingestion, inhalation, and dermal contact. The digestive system is important in the digestion and absorption of nutrients and electrolytes, which occur mainly in the small intestine. The small intestine may also play an important role in the absorption of microplastics (Figure 1). Contact of microplastics with the intestinal mucosa is dependent on their ability to cross the intestinal mucus, facilitated through a formation of a corona of organic matter or intestinal contents (Powell et al., 2007) or due to small particle sizes (Szentkuti, 1997). After crossing the intestinal mucus, particles come in contact with the intestinal epithelium, being internalized by the following mechanisms: (i) transcytosis, the uptake and transport of smaller particles by enterocytes; (ii) internalization by M cells (e.g. micropinocytosis, phagocytosis, and receptor-mediated endocytosis) or other cells in the intestinal mucosa adjacent to Peyer’s patches; (iii) paracellular transport, through gaps between cells dependent on concentration gradients and particle sizes, increasing when tight junction integrity is compromised; (iv) persorption through gaps in the villi during cell turnover (desquamation zones), openings of tight junctions during the migration of macrophages, or damage to the epithelium (e.g. erosion and ulceration), for larger particles (e.g. 7–70 µm); (v) uptake by migratory phagocytes (e.g. intestinal macrophages and dendritic cells) directly from the intestinal lumen (Delon et al., 2022).
Potential adverse health effects of ingested micro- and nanoplastics on humans. Lessons learned from in vivo and in vitro mammalian models
Published in Journal of Toxicology and Environmental Health, Part B, 2020
Laura Rubio, Ricard Marcos, Alba Hernández
From the existing mechanisms of particle uptake in the intestine, internalization via “M” cells and persorption were described as the most likely mechanisms responsible for MPs uptake, due to the extensive range of MP sizes that the intestine is able to absorb (Wright and Kelly 2017). “M” cells, forming 5 to 10% of cells in Peyer’s patches in humans, are able to take up large amounts of material up to 10 µm from the lumen by endocytosis, and transport this material to the “lamina propia” linked to lymph nodes and, eventually, to the blood system (Eldridge et al. 1989; Kucharzik et al. 2000). An alternative mechanism permitting the internalization of large particles through the small intestine is by persorption. By this mechanism, particles up to 150 µm cross the cellular barrier through gaps in the epithelium, known as desquamation zones (Steffens 1995).