Interleukin-18 (IL-18）is a protein which belongs to the IL-1 family. It is expressed as a 24 kDa precursor by endothelial and epithelial cells, keratinocytes, gamma δ T cells, and phagocytes. Mature mouse IL-18 shares 63% and 91% amino acid sequence identity with mouse and rat IL-18, respectively. IL-18 binds to the widely expressed IL-18 R alpha which recruits IL-18 R beta to form the signaling receptor complex. Its bioactivity is negatively regulated by interactions with IL-18 binding proteins and virally encoded IL-18BP homologs. It augments natural killer cell activity in spleen cells and stimulates interferon gamma production in T-helper type I cells. In the presence of IL-12 or IL-15, IL-18 enhances anti-viral Th1 immune responses by inducing IFN-gamma production and the cytolytic activity of CD8+ T cells and NK cells. In the absence of IL-12 or IL-15, however, IL-18 promotes production of the Th2 cytokines IL-4 and IL-13 by CD4+ T cells and basophils.

Interleukin (IL)-18 was originally discovered as a factor that enhanced IFN-γ production from anti-CD3-stimulated Th1 cells, especially in the presence of IL-12. Upon stimulation with Ag plus IL-12, naïve T cells develop into IL-18 receptor (IL-18R) expressing Th1 cells, which increase IFN-γ production in response to IL-18 stimulation.

IL-18 Protein, Canine, Recombinant (His) is expressed in E. coli.

IL-18 Protein, Human, Recombinant is expressed in E. coli expression system. The predicted molecular weight is 18.2 kDa and the accession number is Q14116-1.

Plays a role as a neuroprotective factor. Protects against neuronal cell death induced by multiple different familial Alzheimer disease genes and amyloid-beta proteins in Alzheimer disease. Mediates its neuroprotective effect by interacting with a receptor complex composed of IL6ST/GP130, IL27RA/WSX1 and CNTFR. Also acts as a ligand for G-protein coupled receptors FPR2/FPRL1 and FPR3/FPRL2. Inhibits amyloid-beta protein 40 fibril formation. Also inhibits amyloid-beta protein 42 fibril formation. Suppresses apoptosis by binding to BAX and preventing the translocation of BAX from the cytosol to mitochondria. Also suppresses apoptosis by binding to BID and inhibiting the interaction of BID with BAX and BAK which prevents oligomerization of BAX and BAK and suppresses release of apoptogenic proteins from mitochondria. Forms fibers with BAX and also with BID, inducing BAX and BID conformational changes and sequestering them into the fibers which prevents their activation. Can also suppress apoptosis by interacting with BIM isoform BimEL, inhibiting BimEL-induced activation of BAX, blocking oligomerization of BAX and BAK, and preventing release of apoptogenic proteins from mitochondria. Plays a role in up-regulation of anti-apoptotic protein BIRC6/APOLLON, leading to inhibition of neuronal cell death. Binds to IGFBP3 and specifically blocks IGFBP3-induced cell death. Competes with importin KPNB1 for binding to IGFBP3 which is likely to block IGFBP3 nuclear import. Induces chemotaxis of mononuclear phagocytes via FPR2/FPRL1. Reduces aggregation and fibrillary formation by suppressing the effect of APP on mononuclear phagocytes and acts by competitively inhibiting the access of FPR2 to APP. Protects retinal pigment epithelium (RPE) cells against oxidative stress-induced and endoplasmic reticulum (ER) stress-induced apoptosis. Promotes mitochondrial biogenesis in RPE cells following oxidative stress and promotes STAT3 phosphorylation which leads to inhibition of CASP3 release. Also reduces CASP4 levels in RPE cells, suppresses ER stress-induced mitochondrial superoxide production and plays a role in up-regulation of mitochondrial glutathione. Reduces testicular hormone deprivation-induced apoptosis of germ cells at the nonandrogen-sensitive stages of the seminiferous epithelium cycle. Protects endothelial cells against free fatty acid-induced inflammation by suppressing oxidative stress, reducing expression of TXNIP and inhibiting activation of the NLRP3 inflammasome which inhibits expression of proinflammatory cytokines IL1B and IL18. Protects against high glucose-induced endothelial cell dysfunction by mediating activation of ERK5 which leads to increased expression of transcription factor KLF2 and prevents monocyte adhesion to endothelial cells. Inhibits the inflammatory response in astrocytes. Increases the expression of PPARGC1A/PGC1A in pancreatic beta cells which promotes mitochondrial biogenesis. Increases insulin sensitivity.

Interleukin-18 is a secreted protein and it belongs to the IL-1 family. IL-18 is a proinflammatory cytokine and produced by macrophages and other cells. This cytokine can induce the IFN-gamma production of T cells. The combination of this cytokine and IL12 has been shown to inhibit IL-4 dependent IgE and IgG1 production, and enhance IgG2a production of B cells. IL-18 binding protein (IL18BP) can specifically interact with this cytokine, and thus negatively regulate its biological activity. After stimulation with IL-18, natural killer (NK) cells and certain T cells release another important cytokine called interferon-γ (IFN-γ) or type II interferon that plays an important role in activating the macrophages or other cells.

IL-18 Protein, Human, Recombinant (GST) is expressed in E. coli expression system with GST tag. The predicted molecular weight is 48.6 kDa and the accession number is Q14116.

Plays a role as a neuroprotective factor. Protects against neuronal cell death induced by multiple different familial Alzheimer disease genes and amyloid-beta proteins in Alzheimer disease. Mediates its neuroprotective effect by interacting with a receptor complex composed of IL6ST/GP130, IL27RA/WSX1 and CNTFR. Also acts as a ligand for G-protein coupled receptors FPR2/FPRL1 and FPR3/FPRL2. Inhibits amyloid-beta protein 40 fibril formation. Also inhibits amyloid-beta protein 42 fibril formation. Suppresses apoptosis by binding to BAX and preventing the translocation of BAX from the cytosol to mitochondria. Also suppresses apoptosis by binding to BID and inhibiting the interaction of BID with BAX and BAK which prevents oligomerization of BAX and BAK and suppresses release of apoptogenic proteins from mitochondria. Forms fibers with BAX and also with BID, inducing BAX and BID conformational changes and sequestering them into the fibers which prevents their activation. Can also suppress apoptosis by interacting with BIM isoform BimEL, inhibiting BimEL-induced activation of BAX, blocking oligomerization of BAX and BAK, and preventing release of apoptogenic proteins from mitochondria. Plays a role in up-regulation of anti-apoptotic protein BIRC6/APOLLON, leading to inhibition of neuronal cell death. Binds to IGFBP3 and specifically blocks IGFBP3-induced cell death. Competes with importin KPNB1 for binding to IGFBP3 which is likely to block IGFBP3 nuclear import. Induces chemotaxis of mononuclear phagocytes via FPR2/FPRL1. Reduces aggregation and fibrillary formation by suppressing the effect of APP on mononuclear phagocytes and acts by competitively inhibiting the access of FPR2 to APP. Protects retinal pigment epithelium (RPE) cells against oxidative stress-induced and endoplasmic reticulum (ER) stress-induced apoptosis. Promotes mitochondrial biogenesis in RPE cells following oxidative stress and promotes STAT3 phosphorylation which leads to inhibition of CASP3 release. Also reduces CASP4 levels in RPE cells, suppresses ER stress-induced mitochondrial superoxide production and plays a role in up-regulation of mitochondrial glutathione. Reduces testicular hormone deprivation-induced apoptosis of germ cells at the nonandrogen-sensitive stages of the seminiferous epithelium cycle. Protects endothelial cells against free fatty acid-induced inflammation by suppressing oxidative stress, reducing expression of TXNIP and inhibiting activation of the NLRP3 inflammasome which inhibits expression of proinflammatory cytokines IL1B and IL18. Protects against high glucose-induced endothelial cell dysfunction by mediating activation of ERK5 which leads to increased expression of transcription factor KLF2 and prevents monocyte adhesion to endothelial cells. Inhibits the inflammatory response in astrocytes. Increases the expression of PPARGC1A/PGC1A in pancreatic beta cells which promotes mitochondrial biogenesis. Increases insulin sensitivity.

Interleukin-18-binding protein, also known as Tadekinig-alfa and IL18BP, contains 1 Ig-like C2-type domain. IL18BP is constitutively expressed and secreted in mononuclear cells. IL18BP functions as an IL18 inhibitor. IL18BP binds to IL18, prevents the binding of IL18 to its receptor, and thus inhibits IL18-induced IFN-gamma production. It has been shown that IL18BP may be a promising molecular approach to inhibit neointimal hyperplasia and arteriosclerosis progression following coronary and peripheral angioplasty.