Editing Mast cell (section)

===Mast cell mediators===
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A unique, stimulus-specific set of mast cell mediators is released through degranulation following the activation of [[cell surface receptor]]s on mast cells.<ref name="Mast cell mediators - eoxins" /> Examples of mediators that are released into the extracellular environment during mast cell degranulation include:<ref name=Prussin/><ref name="Mast cell mediators - eoxins" /><ref name="pmid23600539">{{cite journal | vauthors = Ashmole I, Bradding P | title = Ion channels regulating mast cell biology | journal = Clin. Exp. Allergy | volume = 43 | issue = 5 | pages = 491–502 | date = May 2013 | pmid = 23600539 | doi = 10.1111/cea.12043 | s2cid = 1127584 | quote = P2X receptors are ligand-gated non-selective cation channels that are activated by extracellular ATP.&nbsp;... Increased local ATP concentrations are likely to be present around mast cells in inflamed tissues due to its release through cell injury or death and platelet activation [40]. Furthermore, mast cells themselves store ATP within secretory granules, which is released upon activation [41]. There is therefore the potential for significant Ca2+ influx into mast cells through P2X receptors. Members of the P2X family differ in both the ATP concentration they require for activation and the degree to which they desensitise following agonist activation [37, 38]. This opens up the possibility that by expressing a number of different P2X receptors mast cells may be able to tailor their response to ATP in a concentration dependent manner [37].}}</ref>
* [[serine protease]]s, such as [[tryptase]] and [[chymase]]
* [[histamine]] (2–5&nbsp;[[picogram]]s per mast cell)
* [[serotonin]]
* [[proteoglycan]]s, mainly [[heparin]] (active as [[anticoagulant]]) and some [[chondroitin sulfate proteoglycan]]s
* [[adenosine triphosphate]] (ATP)
* [[lysosomal enzymes]]
** [[Hexosaminidase|β-hexosaminidase]]
** [[β-glucuronidase]]
** [[arylsulfatase]]s
* newly formed lipid mediators ([[eicosanoid]]s):
** [[thromboxane]]
** [[prostaglandin D2]]
** [[leukotriene C4]]
** [[platelet-activating factor]]
* [[cytokine]]s
** [[TNF-α]]
** [[basic fibroblast growth factor]]
** [[interleukin-4]]
** [[stem cell factor]]
** [[chemokine]]s, such as [[eosinophil chemotactic factor]]
* [[reactive oxygen species]]

[[Image:Histamine.svg|thumb|right|250px|Structure of histamine]]
Histamine dilates post-capillary venules, [[endothelial activation|activates the endothelium]], and increases blood vessel permeability. This leads to local [[edema]] (swelling), warmth, redness, and the attraction of other inflammatory cells to the site of release. It also depolarizes [[nerve ending]]s (leading to [[itching]] or [[pain]]). Cutaneous signs of histamine release are the "flare and [[wheal response|wheal]]"-reaction. The bump and redness immediately following a mosquito bite are a good example of this reaction, which occurs seconds after challenge of the mast cell by an allergen.<ref name=Prussin/>

The other physiologic activities of mast cells are much less-understood. Several lines of evidence suggest that mast cells may have a fairly fundamental role in [[innate immunity]]: They are capable of elaborating a vast array of important cytokines and other inflammatory mediators such as TNF-α; they express multiple "pattern recognition receptors" thought to be involved in recognizing broad classes of pathogens; and mice without mast cells seem to be much more susceptible to a variety of infections.{{Citation needed|date=June 2007}}

Mast cell granules carry a variety of bioactive chemicals. These granules have been found to be transferred to adjacent cells of the immune system and [[neurons]] in a process of transgranulation via mast cell [[pseudopodia]].<ref name="pmid16262662">{{cite journal |vauthors=Wilhelm M, Silver R, Silverman AJ |title=Central nervous system neurons acquire mast cell products via transgranulation |journal=The European Journal of Neuroscience |volume=22 |issue=9 |pages=2238–48 |date=November 2005  |pmid=16262662 |pmc=3281766 |doi=10.1111/j.1460-9568.2005.04429.x}}</ref>