Human tumor necrosis factor alpha (TNF-), also known as tumor necrosis factor ligand superfamily member 2 (TNFSF2) and cachectin, is a 25.6 kDa cytokine. TNF is a transmembrane protein that oligomerizes intracellularly to form a non-covalent homotrimer. The membrane-bound soluble portion of the homotrimer is cleaved by TACE/ADAM17 to form TNF-. The homotrimer binds to the receptors TNF RI and TNF RII, both of which are also expressed as homotrimers. TNF- is mainly secreted by macrophages and can induce apoptosis in some tumor cell lines. It stimulates IL-1, which induces cachexia and causes fever. The intracellular form of TNF induces IL-12 production in dendritic cells. It can induce sepsis and inflammation and can inhibit tumorigenesis and viral replication. The Human TNF- Kit provides assay-specific components for the quantitative determination of endogenous TNF- in human urine, serum, plasma, and cell culture supernatants.