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The innate immune system is made of non-specific defensive mechanisms against foreign cells inside the host including skin as a physical barrier to entry, activation of the complement cascade to identify foreign bacteria and activate necessary cell responses, and white blood cells that remove foreign substances.
Antigens are recognized via expression of cell surface receptors such as glycoprotein-2 (GP2) that detect and specifically bind to bacteria. Cellular prion protein (PrP) is another example of a cell surface receptor on M cells. [2] M cells lack microvilli but, like other epithelial cells, they are characterized by strong cell junctions. This ...
Rather, NK cells destroy compromised host cells, such as tumor cells or virus-infected cells, recognizing such cells by a condition known as "missing self". This term describes cells with abnormally low levels of a cell-surface marker called MHC I ( major histocompatibility complex ) - a situation that can arise in viral infections of host ...
The NETs are released as the cell membrane breaks, resulting in a unique process of cell death. These NET structures of neutrophils bind Gram-positive and Gram-negative bacteria, as well as fungi, which confers broad specificity of neutrophils, explaining their role in the first line of defense once microbes have invaded. [10]
Rather, NK cells destroy compromised host cells, such as tumor cells or virus-infected cells, recognizing such cells by a condition known as "missing self". This term describes cells with low levels of a cell-surface marker called MHC I (major histocompatibility complex)—a situation that can arise in viral infections of host cells. [42]
[2] [3] For example, the B cell line in the intestinal mucosa is regulated by extracellular signals from commensal microbes that affect the intestinal immunoglobulin repertoire. [19] Diversity of microbiota in early childhood protects the body from the induction of mucosal IgE , which is associated with allergy development.
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.
An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellular bacteria, protozoa, helminths, and fungi which could cause serious problems to the health of the host organism if not cleared from the body.