This entry represents interleukin-23 subunit alpha, IL-23A (also known as Interleukin-23 subunit p19) associates with IL-12B to form the IL-23 interleukin, a heterodimeric cytokine which functions in innate and adaptive immunity []. IL-23 may constitute with IL-17 an acute response to infection in peripheral tissues. IL-23 binds to a heterodimeric receptor complex composed of IL12RB1 and IL23R, activates the Jak-Stat signaling cascade, stimulates memory rather than naive T-cells and promotes production of proinflammatory cytokines. IL-23 induces autoimmune inflammation and thus may be responsible for autoimmune inflammatory diseases and may be important for tumorigenesis []. Similar to IL-12, human IL-23 stimulates IFN-gamma production and proliferation in PHA blast T cells, as well as in CD45RO (memory) T cells [].
A number of receptors for lymphokines, hematopoietic growth factors and growth hormone-related molecules have been found to share a common binding domain. These receptors are designated as hematopoietin receptors []and the corresponding ligands as hematopoietins. Further, hematopoietins have been subdivided into two major structural groups: Large/long and small/short hematopoietins.One subset of individual receptor chains that are part of receptor complexes for large hematopoietins contain common structural elements in their extracellular parts: an immunoglobulin-like domain, an hematopoietin-receptor domain, and 3 fibronectin type-III domains (2 in the leptin receptor). This subgroup was designated as "Gp130 family of receptors"[]and contains the following chains: Leptin receptor (LPTR), Granulocyte colony stimulating factor receptor (GCSFR), Interleukin-6/-11/LIF/OSM/CNTF common beta chain (Gp130), Leukemia inhibiting factor receptor (LIFR), Oncostatin-M receptor beta chain (OSMR), Interleukin-12 receptor beta-1 chain (IL12RB1), Interleukin-12 receptor beta-2 chain (IL12RB2). A schematic representation of the structure of these receptors is shown below: +-------+-------------------------+-----------------xxxxxxx-----------------+|Ig-like| C C C C Extracellular | FnIII (x3) XXXXXXX Cytoplasmic |+-------+-|-|--|--|---------------+-----------------xxxxxxx-----------------+| | | | Transmembrane+-+ +--+These receptor chains homodimerize (GCSFR, Gp130, LPTR) or heterodimerize (Gp130 with LIFR or OSMR, IL12RB1 with IL12RB2) upon binding of the cognate cytokine: G-CSF, LIF, OSM, LPT, or the cytokine/alpha chain complex: IL-6/IL6RA, IL-11/IL11RA, CNTF/CNTFRA, IL-12 (p35/p40) [, ].
