IL-18 Antibody

Interleukin-18 (IL-18) is a member of the IL-1 cytokine family and was initially identified as an Interferon-g (IFN-g) inducing factor (IGIF). The IL-18 gene was originally cloned from liver cells and has since been shown to be produced by activated monocytes/ macrophages, Kupffer cells, keratinocytes, glucocorticoid-secreting adrenal cortex cells, osteoblasts and dendritic cells. IL-18 is a 24 kDa, non-glycosylated polypeptide that lacks a classical signal sequence and possesses a structure recognizably similar to IL-1.  IL-18 is synthesized as a bio-inactive propeptide that undergoes proteolytic cleavage by either ICE (interleukin-1 beta converting enzyme) or another caspase to generate a mature, bioactive, 18 kDa molecule.  In both the mature and propeptide forms, IL-18 shows 64% aa sequence identity from mouse to human.  IL-18 does not appear to show any primary sequence similarity to any other known cytokines.  Rat IL-18 has also been isolated, and found to be 194 aa in length with a 91% aa sequence identity to mouse IL-18.  Human IL-18 has been found to induce the production of IFN-g and GM-CSF while inhibiting the production of IL-10 by PBMC.  With respect to human T cells, IL-18 enhances Th1 cytokine production and stimulates cell proliferation via an IL-2-dependent pathway.  Human IL-18 can also inhibit the synthesis of IgE by B cells. Thus, IL-18 plays an important role in immunological and inflammatory reactions. Currently, the bioactivity of human IL-18 is often determined by its capacity to augment the levels of IFN-g produced by T cells as measured in tissue culture supernatants.