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Mast cells are especially numerous at sites of potential injury – the nose, mouth, and feet, internal body surfaces, and blood vessels. Non-mast cell histamine is found in several tissues, including the hypothalamus region of the brain, where it functions as a neurotransmitter.
For example, the typical itching felt around a healing scab may be caused by histamine released by mast cells. Researchers also think mast cells may have a role in the growth of blood vessels (angiogenesis). No one with too few or no mast cells has been found, which indicates to some scientists we may not be able to survive with too few mast cells.
Histamine is a small molecule, stored in granules of mast cells and basophils. Mast cells and basophils are the effector cells involved in the immediate hypersensitivity response. Found in tissues throughout the body, they are particularly associated with blood vessels and nerves, and are in proximity to surfaces that border the external ...
Mast cells are present in most tissues characteristically surrounding blood vessels, nerves and lymphatic vessels, [11] and are especially prominent near the boundaries between the outside world and the internal milieu, such as the skin, mucosa of the lungs, and digestive tract, as well as the mouth, conjunctiva, and nose. [7]
Mast cells, a type of white blood cell, also contribute to the paracrine regulation of blood flow by releasing histamine. During an immune response, histamines are released by the mast cells and stimulate the endothelial cells to produce nitric oxide and prostacyclin. Again, this signals the relaxation of the vascular smooth muscle tissue ...
Histamine is a weak base (a compound able to react with a hydrogen ion to form an acid) that can link with acid groups within the granules of the mast cells. [8] The mechanism of the displacement theory. The crux of this theory lies in the assumption that histamine liberators release histamine by displacing it from cells.
The histamine receptors are a class of G protein–coupled receptors which bind histamine as their primary endogenous ligand. [1] [2] Histamine receptors are proteins that bind with histamine, a neurotransmitter involved in various physiological processes. There are four main types: H1, H2, H3, and H4.
Finally, H 4 plays roles in mast cell chemotaxis and cytokine production. [17] In humans, HDC is primarily expressed in mast cells and basophil granulocytes. Accordingly, these cells contain the body's highest concentrations of histamine granules. Non-mast cell histamine is also found in the brain, where it is used as a neurotransmitter. [21]