Mast cells

A mast cell (or mastocyte) is a resident cell of areolar connective tissue (loose connective tissue) that contains many granules rich in histamine and heparin. Although best known for their role in allergy and anaphylaxis, mast cells play an important protective role as well, being intimately involved in wound healing and defense against pathogens. Image File history File links Download high resolution version (885x682, 87 KB) Summary I took this photo of skin mast cells at 100X using an oil immersion lens and an olympus digital camera. ... Image File history File links Download high resolution version (885x682, 87 KB) Summary I took this photo of skin mast cells at 100X using an oil immersion lens and an olympus digital camera. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hook from Micrographia which is the origin of the word cell. POOP Cells in culture, stained for keratin (red) and DNA (green). ... Gel-like matrix with all three fiber types Areoloar tissue is the most common connnective tissue type and can be found in the skin as well as in places that connect epithelium to other tissues. ... This article or section does not cite any references or sources. ... Heparin, a highly sulfated glycosaminoglycan is widely used as an injectable anticoagulant and has the highest negative charge density of any known biological molecule. ... This article deals specifically with IgE-mediated hypersensitivity. ... }} In medicine, anaphylaxis is a severe and rapid multi-system allergic reaction. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ...

Origin and classification

Mast cell

Mast cells were first described by Paul Ehrlich in 1878 on the basis of their unique staining characteristics and large granules. These granules also led him to the mistaken belief that they existed to nourish the surrounding tissue, and he named them "mastzellen," meaning "feeding-cells." Nowadays, they are considered part of the immune system. Mast cells are very similar to basophil granulocytes (a class of white blood cells) in blood; the similarities between mast cells and basophils has led many to speculate that mast cells are basophils that have "homed in" on tissues. However, current evidence suggests that they are generated by different precursor cells in the bone marrow. Nevertheless, both mast cells and basophils are thought to originate from bone marrow precursors expressing the CD34 molecule. The basophil leaves the bone marrow already mature while the mast cell circulates in an immature form, only maturing once in a tissue site. The tissue site an immature mast cell chooses to settle in probably determines its precise characteristics. Image File history File links Mast_cell. ... Image File history File links Mast_cell. ... Paul Ehrlich Paul Ehrlich in his workroom Paul Ehrlich (March 14, 1854 – August 20, 1915) was a German scientist who won the 1908 Nobel Prize in Physiology or Medicine. ... 1878 (MDCCCLXXVIII) was a common year starting on Tuesday (see link for calendar). ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... This article or section does not cite its references or sources. ... A scanning electron microscope image of normal circulating human blood. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... Grays Anatomy illustration of cells in bone marrow. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...

Two types of mast cells are recognised, those from connective tissue and a distinct set of mucosal mast cells. The activities of the latter are dependent on T-cells. Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue. ... The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. ... T cells belong to a group of white blood cells known as lymphocytes and play a central role in cell-mediated immunity. ...

Mast cells are present in most tissues in the vicinity of blood vessels, 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 in the mouth, conjunctiva and nose. In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs. ... Respiratory system The lungs flank the heart and great vessels in the chest cavity. ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... It has been suggested that this article or section be merged with mouth (human). ... The conjunctiva is a membrane that covers the sclera (white part of the eye) and lines the inside of the eyelids. ... For the article about nose in humans, see human nose Human nose in profile Elephants have prehensile noses Dogs have very sensitive noses Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth. ...

Physiology

Mast cells play a key role in the inflammatory process. When activated, a mast cell rapidly releases its characteristic granules and various hormonal mediators into the interstitium. Mast cells can be stimulated to degranulate by direct injury (e.g physical or chemical), cross-linking of IgE receptors, or by activated complement proteins. The degranulation process in a Mast cell. ...

Mast cells express a high-affinity receptor (FcεRI) for Immunoglobulin E (IgE), the least-abundant member of the antibodies. This receptor is of such high affinity that binding of IgE molecules is essentially irreversible. As a result, mast cells are coated with IgE. IgE is produced by B-cells (the antibody-producing cells of the immune system). IgE molecules, like all antibodies, are specific to one particular antigen. FcεRI, or Fc epsilon RI, is the high-affinity receptor for immunoglobulin E (IgE), an antibody isotype involved in allergy and (arguably) resistance to parasites. ... Immunoglobulin E (IgE) is an antibody subclass (known as isotypes), found only in mammals. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... An antigen is a molecule that stimulates an immune response. ...

The role of mast cells in the development of allergy.

In allergic reactions, mast cells remain inactive until an allergen binds to IgE already in association with the cell (see above). Allergens are generally proteins or polysaccharides. The allergen binds to the Fab part of the IgE molecules on the mast cell surface. It appears that binding of two or more IgE molecules (this is called crosslinking) is required to activate the mast cell; the steric changes lead to a slight disturbance to the cell membrane structure, causing a complex sequence of reactions inside the cell that lead to activation of the cell. Although this reaction is most well understood in terms of allergy, it appears to have evolved as a defense system against intestinal worm infestations (tapeworms, etc). Image File history File links Download high-resolution version (634x1138, 375 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Mast cell Immunoglobulin E ... Image File history File links Download high-resolution version (634x1138, 375 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Mast cell Immunoglobulin E ... An allergen is any substance (antigen), most often eaten or inhaled, that is recognized by the immune system and causes an allergic reaction. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Polysaccharides (sometimes called glycans) are relatively complex carbohydrates. ... ...

The molecules thus released into the intercellular environment include:

• preformed mediators (from the granules):
  • histamine (2-5 pg/cell)
  • proteoglycans, mainly heparin (active as anticoagulant)
  • serine proteases
• newly formed lipid mediators (eicosanoids):
  • prostaglandin D2
  • leukotriene C4
• cytokines

Histamine dilates post capillary venules, 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 irritates nerve endings (leading to itching or pain). Cuteanous signs of histamine release are the "flare and 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. This article or section does not cite any references or sources. ... The picogram is an SI unit of mass (symbol pg) defined as: 1 pg = 1 × 10-15 kilogram (1 × 10-12 gram) A picogram is one trillionth (1/1000000000000) of a gram. ... Heparin, a highly sulfated glycosaminoglycan is widely used as an injectable anticoagulant and has the highest negative charge density of any known biological molecule. ... An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. ... Crystal structure of Trypsin, a typical serine protease. ... In biochemistry, eicosanoids are a class of oxygenated hydrophobic molecules that largely function as autocrine and paracrine mediators. ... Prostaglandin D2 is a prostaglandin which binds to the receptor PTGDR.      Eicosanoids: prostaglandins D2 - Alprostadil (E1) - Dinoprostone (E2) - H2 - Prostacyclin (I2) Prostaglandin analogues: Beraprost - Bimatoprost - Carboprost - Enprostil - Iloprost - Latanoprost - Misoprostol - Travoprost - Treprostinil Category: ... Leukotrienes are autocrine and paracrine eicosanoid lipid mediators derived from arachidonic acid by 5-lipoxygenase. ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... The endothelium is the layer of thin, flat cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. ... Edema (American English) or oedema (British English), formerly known as dropsy or hydropsy, is swelling of any organ or tissue due to accumulation of excess lymph fluid, without an increase of the number of cells in the affected tissue. ... A nerve is an enclosed, cable-like bundle of nerve fibers or axons, which includes the glia that ensheath the axons in myelin. ... An itch (Latin: pruritus) is a sensation felt on an area of skin that makes a person or animal want to scratch it. ... Hurting redirects here. ... The word wheal could refer to: Look up wheal in Wiktionary, the free dictionary. ...

Structure of histamine

The other physiologic activities of mast cells are much less well-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, 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. Histamine diagram This image is generated from the SMILES formula [N][C][C]C1=[C]N=[C][N]1 at http://daylight. ... Histamine diagram This image is generated from the SMILES formula [N][C][C]C1=[C]N=[C][N]1 at http://daylight. ... Innate immunity is immunity that the body possesses naturally, as opposed to adaptive immunity. ...

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 via transgranulation via their pseudopodia.^{[citation needed]} Neurons (also called nerve cells) are the primary cells of the nervous system. ... Pseudopods or pseudopodia (false feet) are temporary projections of eukaryotic cells. ...

Role in disease

Allergic disease

Many forms of cutaneous and mucosal allergy are mediated for a large part by mast cells; they play a central role in asthma, eczema, itch (from various causes) and allergic rhinitis and allergic conjunctivitis. Antihistamine drugs act by blocking the action of histamine on nerve endings. Cromoglicate-based drugs (sodium cromoglicate, nedocromil) block a calcium channel essential for mast cell degranulation, stabilizing the cell and preventing release of histamine and related mediators. Leukotriene antagonists (such as montelukast and zafirlukast) block the action of leukotriene mediators, and are being used increasingly in allergic diseases. This article deals specifically with IgE-mediated hypersensitivity. ... Eczema is a form of dermatitis, or inflammation of the upper layers of the skin. ... An itch (Latin: pruritus) is a sensation felt on an area of skin that causes a person or animal to desire to scratch that area. ... For the play, see Hay Fever. ... Allergic conjunctivitis is irritation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. ... An antihistamine is a drug which serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions, through action at the histamine receptor. ... This article or section does not cite any references or sources. ... Cromoglicate (INN) (also referred to as cromolyn (USAN) or cromoglycate (former BAN)) is traditionally described as a mast cell stabilizer, and is commonly marketed as the sodium salt sodium cromoglicate. ... Leukotrienes are autocrine and paracrine eicosanoid lipid mediators derived from arachidonic acid by 5-lipoxygenase. ... Montelukast is an oral leukotriene receptor antagonist (LTRA) for the maintenance treatment of asthma and to relieve symptoms of seasonal allergies. ... Zafirlukast is an oral leukotriene receptor antagonist (LTRA) for the maintenance treatment of asthma. ...

Anaphylaxis

In anaphylaxis (a severe systemic reaction to allergens, such as nuts, bee stings or drugs), body-wide degranulation of mast cells leads to vasodilation and, if severe, symptoms of life-threatening shock. }} In medicine, anaphylaxis is a severe and rapid multi-system allergic reaction. ... An allergen is any substance (antigen), most often eaten or inhaled, that is recognized by the immune system and causes an allergic reaction. ... This article is about the medical condition. ...

Immunity

Mast cells are implicated in the pathology associated with the autoimmune disorders rheumatoid arthritis, bullous pemphigoid, and multiple sclerosis. They have been shown to be involved in the recruitment of inflammatory cells to the joints (e.g. rheumatoid arthritis) and skin (e.g. bullous pemphigoid) and this activity is dependent on antibodies and complement components. Mast cells are also integral to the innate immune response and are important for clearance of bacteria and viruses. Rheumatoid arthritis (RA) is traditionally considered a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. ... Bullous pemphigoid, also referred to as BP, is a chronic autoimmune skin disease, involving the formation of blisters below the surface of the skin and antibodies against collagen XVII. It can also (albeit only rarely) involve the mucous membranes, and has been shown to afflict dogs, cats, pigs, and horses... Rheumatoid arthritis (RA) is traditionally considered a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. ...

Mast cell disorders

Mastocytosis is a rare condition featuring proliferation of mast cells. It exists in a cutaneous and systemic form, with the former being limited to the skin and the latter involving multiple organs. Mast cell tumors are often seen in dogs and cats. Mast cells play a key role in tumor formation in Neurofibromatosis Type I^[1] In medicine, mastocytosis is a group of rare disorders of both children and adults caused by the presence of too many mast cells (mastocytes) in a persons body. ... A mast cell tumor is a type of tumor consisting of mast cells that is found in many species of animals. ...

Sources

• Prussin C, Metcalfe DD. IgE, mast cells, basophils, and eosinophils. J Allergy Clin Immunol 2003;111(2 Suppl):S486-94. PMID 12592295.
• Wilhelm, M., Silver, R., Silverman, A.J. (2005). Central nervous system neurons acquire mast cell products via transgranulation. European Journal of Neuroscience 22:2238-2248.

References

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1. ^ *Feng-Chun Yang, Shi Chen, Travis Clegg, Xiaohong Li, Trent Morgan, Selina A. Estwick, Jin Yuan, Waleed Khalaf, Sarah Burgin, Jeff Travers, Luis F. Parada, David A. Ingram and D. Wade Clapp,* . "Nf1+/– mast cells induce neurofibroma like phenotypes through secreted TGF-ß signaling", Human Molecular Genetics, July 11, 2006. Accessed May 25, 2005.

> July 11 is the 192nd day (193rd in leap years) of the year in the Gregorian calendar, with 173 days remaining. ... For the Manfred Mann album, see 2006 (album). ... May 25 is the 145th day of the year (146th in leap years) in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

External links

• MeSH Mast+cells