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© Dirk Biddle
Eosinophils reside predominantly in
submucosal tissue and are recruited to sites of specific immune reactions, including allergic reactions. They are
motile and
phagocytic and are particularly active in parasitic infection where they kill antibody coated parasites. They contain many crystal granules in their cytoplasm, including major basic protein (MBP), eosinophil cationic protein (ECP),
eosinophil derived neurotoxin (EDN), and
eosinophil peroxidase (EPO). These molecules are toxic to many organisms (and also to host tissues). However, MBP, by a non-
cytotoxic mechanism, can also stimulate the release of
histamine from basophils and histamine and EPO from mast cells.
Eosinophils also participate in
hypersensitivity immune responses, especially through two
lipid inflammatory mediators,
leucotriene C4 and platelet activating factor (PAF). Both mediators contract airway smooth muscle, promote the secretion of mucus, alter vascular permeability and elicit eosinophil and neutrophil infiltration into the vascular walls. The eosinophil is characteristically present in lesions of patients with Churg-Strauss syndrome.
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Submucosa: A supporting layer of loose connective tissue directly under a mucous membrane -- called also tela submucosa. (M+)
Motile: Capable of movement
Phagocyte: A cell such as a white blood cell that engulfs and consumes foreign material (eg: micro-organisms) and debris. (OMD)
Antibody: Any of a large number of proteins of high molecular weight that are produced normally by specialized B-cells after stimulation by an antigen and act specifically against the antigen in an immune response, that are produced abnormally by some cancer cells, and that typically consist of four subunits including two heavy chains and two light chains - called also immunoglobulin. (M+
Cytoplasm: The organized complex of inorganic and organic substances external to the nuclear membrane of a cell and including the cytosol and membrane-bound organelles (such as mitochondria, lysosomes, ribosomes). (OMD)
Major Basic Protein: A toxic cationic protein that is the principal protein found in the granules of eosinophils and that is capable of damaging tissue (as of the eye) if released into extracellular spaces. (M+)
Eosinophil Cationic Protein: Arginine rich protein (21 kD) in granules of eosinophils, that damages schistosomula in vitro. Not the same as the MBP (major basic protein) of the granules. (OMD)
Eosinophil Derived Neurotoxin: Neurotoxin:
A substance, often exquisitely toxic, that inhibits neuronal function. Neurotoxins act typically against the sodium channel (e.g. tetrdotoxin - TTX) or block or enhance synaptic transmission (curare, bungarotoxin). (OMD)
Cytotoxic: (cell poison) Chemicals that are directly toxic to cells, preventing their reproduction or growth. Cytotoxic agents can, as a side effect, damage healthy, non-cancerous tissues or organs which have a high proportion of actively dividing cells, for example, bone marrow, hair follicles. These side effects limit the amount and frequency of drug administration. (OMD)
Histamine: Formed by decarboxylation of histidine. Potent pharmacological agent acting through receptors in smooth muscle and in secretory systems.
Stored in mast cells and released by antigen. (See hypersensitivity). Responsible for the early symptoms of anaphylaxis. Also present in some venoms. (M+)
A compound C5H9N3 especially of mammalian tissues that causes dilatation of capillaries, contraction of smooth muscle, and stimulation of gastric acid secretion, that is released during allergic reactions. (OMD)
Hypersensitive: 1 : excessively or abnormally sensitive
2 : abnormally susceptible physiologically to a specific agent (as a drug or antigen). (M+)
Lipid: Any of a heterogeneous group of fats and fatlike substances characterised by being water insoluble and being extractable by nonpolar (or fat) solvents such as alcohol, ether, chloroform, benzene, etc. All (lipids) contain as a major constituent aliphatic hydrocarbons. The lipids, which are easily stored in the body, serve as a source of fuel, are an important constituent of cell structure and serve other biological functions. Lipids may be considered to include fatty acids, neutral fats, waxes and steroids. Compound lipids comprise the glycolipids, lipoproteins and phospholipids. (OMD)
Leucotriene C4: Leucotriene C4 (LTC4) is one of the highest affinity substrates of the multiple drug resistance protein 1 (MRP1 or ABCC1) which transports anticancer drugs and normal cell metabolites.
PAF: Platelet-activating factor:
Phospholipid that is produced especially by mast cells and basophils. Causes the aggregation of blood platelets and the release of blood-platelet substances (as histamine or serotonin) and is a mediator of inflammation (as in asthma). (OMD)
Potent phospholipid activator and mediator of many leucocyte functions, including platelet aggregation, inflammation, and anaphylaxis.
Synonym: platelet-aggregating factor.