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This provides a physical barrier that constitutes an important line of defense between the gut contents and the immune system of the host. Despite the epithelial barrier, some antigens are able to infiltrate the M cell barrier and infect the nearby epithelial cells or enter the gut. [3]
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 mucosal immune system consists of a cellular component, humoral immunity, and defense mechanisms that prevent the invasion of microorganisms and harmful foreign substances into the body. These defense mechanisms can be divided into physical barriers ( epithelial lining , mucus , cilia function , intestinal peristalsis , etc.) and chemical ...
The mucosa-associated lymphoid tissue (MALT), also called mucosa-associated lymphatic tissue, is a diffuse system of small concentrations of lymphoid tissue found in various submucosal membrane sites of the body, such as the gastrointestinal tract, nasopharynx, thyroid, breast, lung, salivary glands, eye, and skin.
Intraepithelial lymphocytes (IEL) are lymphocytes found in the epithelial layer of mammalian mucosal linings, such as the gastrointestinal (GI) tract and reproductive tract. [1] However, unlike other T cells, IELs do not need priming. Upon encountering antigens, they immediately release cytokines and cause killing of infected target cells.
The intestinal mucosal barrier is a heterogeneous entity composed of physical, biochemical, and immune elements elaborated by the intestinal mucosa. The central component is the intestinal epithelial layer, which provides physical separation between the lumen and the body.
The innate immune system or nonspecific immune system [1] is one of the two main immunity strategies in vertebrates (the other being the adaptive immune system). The innate immune system is an alternate defense strategy and is the dominant immune system response found in plants , fungi , prokaryotes , and invertebrates (see Beyond vertebrates ).
The gastrointestinal tract is composed of numerous cell types that are important for immune activation and barrier surface defenses. The gastrointestinal epithelium is composed of enterocytes, goblet cells, Paneth cells, enteroendocrine cells, tuft cells, and stem cells.