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The gut-associated lymphoid tissue lies throughout the intestine, covering an area of approximately 260–300 m 2. [5] In order to increase the surface area for absorption, the intestinal mucosa is made up of finger-like projections (), covered by a monolayer of epithelial cells, which separates the GALT from the lumen intestine and its contents.
The appendix, long misunderstood as a vestigial organ, is now recognized as a key MALT structure, playing an essential role in B-lymphocyte-mediated immune responses, hosting extrathymically derived T-lymphocytes, regulating pathogens through its lymphatic vessels, and potentially producing early defenses against diseases. [1]
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. [1] Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), [2] [3] and innate lymphoid cells (ILCs; "innate T cell-like" cells involved in mucosal immunity and homeostasis), of which natural killer cells are an ...
The inactive B and T cells are so featureless with few cytoplasmic organelles and mostly inactive chromatin that until the 1960s textbooks could describe these cells, now the central focus of immunology, as having no known function! [11] However, T and B lymphocytes are very distinct cell lineages and they ‘grow up’ in different places in ...
Peyer's patches (or aggregated lymphoid nodules) are organized lymphoid follicles, named after the 17th-century Swiss anatomist Johann Conrad Peyer. [1] They are an important part of gut associated lymphoid tissue usually found in humans in the lowest portion of the small intestine, mainly in the distal jejunum and the ileum, but also could be detected in the duodenum.
These M cells then alert the B cells and T cells in the tonsil that a pathogen is present and an immune response is stimulated. [6] B cells are activated and proliferate in areas called germinal centers in the tonsil. These germinal centers are places where B memory cells are created and secretory antibody (IgA) is produced.
The function of CD4CD8aa IELs is due to their CD8 phenotype and granzyme B expression to prevent pathogens from invading and to maintain integrity of the intestinal epithelial barrier. Their CD4 phenotype is responsible for IL-10 and TGF-β secretion that prevents Th1-induced inflammation in the intestine, therefore their role can be ...
M cells do not secrete mucus or digestive enzymes, and have a thinner glycocalyx, which allows them to have easy access to the intestinal lumen for endocytosis of antigens. The main function of M cells is the selective endocytosis of antigens, and transporting them to intraepithelial macrophages and lymphocytes, which then migrate to lymph ...