Biological or Clinical Significance:
Interleukin 18 (IL-18) is an 18kDa novel cytokine, which has been identified as a co-stimulatory factor for production of interferon-gamma (IFN- γ) in response to toxic shock. It shares functional similarities with IL-12. IL-18 is synthesized as a precursor 24kDa molecule without a signal peptide and must be cleaved to produce an active molecule. It has been reported that IL-18 is produced from Kupffer cells, activated macrophages, keratinocytes, intestinal epithelial cells, osteoblasts, adrenal cortex cells and murine diencephalon.
IL-18 acts on T helper 1-type T (Th1) cells and, in combination with IL-12, strongly induces production of IFN- γ by these cells. Pleiotropic effects of IL-18 have also been reported, including enhancement of IFN- γ and granulocyte macrophage colony-stimulating factor (GM-CSF) production in peripheral blood mononuclear cells, production of T helper type 1 cytokines, IL-2, GM-CSF and IFN- γ in T cells, and enhancement of Fas ligand expression by T helper type 1 cells.
Principle of Test Method:
The IL-18 assay is a sandwich immunoassay using electrochemiluminescent detection.