Interleukin-8 (IL-8) is a chemokine produced by macrophages and other cell types such as epithelial cells. It is also synthesized by endothelial cells, which store IL-8 in their storage vesicles, the Weibel-Palade bodies.
There are more receptors of the surface membrane capable to bind IL-8. The most frequently studied types are the G protein coupled serpentine receptors CXCR1 and CXCR2. Expression and affinity to IL-8 is different in the two receptors (CXCR1>CXCR2). Toll-like receptors are the receptors of the innate immune system. These receptors recognize antigen patterns (like LPS in gram negative bacteria). Through a chain of biochemical reactions IL-8 is secreted and is an important mediator of the immune reaction in the innate immune system response.
It is also secreted in urinary tract infections.
Target cells
While neutrophil granulocytes are the primary target cells of IL-8 there is a relative wide range of cells (endothelial cells, macrophages, mast cells, keratinocytes) responding to this chemokine, too. The chemoattractant activity of IL-8 in similar concentrations to vertebrates was proved in Tetrahymena pyriformis, which refers to a phylogenetically well conserved structure and function in the case of this chemokine.Function
Primary function of IL-8 is the induction of chemotaxis in its target cells (e.g. neutrophil granulocytes). In neutrophils series of cell-physiological responses required for migration and its target function phagocytosis are also induced like increase of intracellular Ca2+, exocytosis (e.g. histamine release), respiratory burst. IL-8 can be secreted by any cells with toll-like receptors which are involved in the innate immune response. IL-8's primary function is to recruit neutrophils to phagocytose the antigen which trigger the antigen pattern toll-like receptors.When first encountering an antigen, the primary cells to encounter it are the macrophages who phagocytose the particle. Upon processing, they release chemokines to signal other immune cells to come in to the site of inflammation. IL-8 is one such chemokine. It serves as a chemical signal that attracts neutrophils at the site of inflammation, and therefore is also known as Neutrophil Chemotactic Factor.
Clinical significance
If a pregnant mother has high levels of interleukin-8, she has a higher risk of inducing schizophrenia in her offspring. High levels of Interleukin 8 have been shown to reduce the chance of good treatment responses to antipsychotic medication in schizophrenia.Interleukin-8 is often associated with inflammation. As an example, it has been cited as a proinflammatory mediator in psoriasis. 
Nomenclature
IL-8 was renamed CXCL8 by the Chemokine Nomenclature Subcommittee of the Nomenclature Committee of the International Union of Immunological Societies, although its approved gene symbol remains IL8.See also
References
Further reading
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Last updated on Monday July 21, 2008 at 17:41:28 PDT (GMT -0700)
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