Tumor necrosis factor-alpha (TNF-alpha), a homotrimeric 17 KD protein, is a potent mediator of inflammatory and metabolic functions. TNF-alpha was originally detected as a highly cytotoxic cytokine for tumor cells, it causes tumor necrosis in vivo and shows cytolytic activity against tumor cells in vitro. Further TNF-alpha has been implied as central mediator in shock induced by gram negative micro-organisms. The cytokine TNF-alpha is found to be a central mediator in many inflammatory and immunological processes: it can be induced by various products of microorganisms and by various cytokines but it also induces on its turn the production of many cytokines. Signal transduction occurs via two types of TNF-receptors, the TNF-receptors I and II. The receptors differ strongly in their intra-cellular signaling pathways. The TNF-alpha trimer interacts with either of the two types of TNF-receptors leading to receptor crosslinking. Synonyms: Cachectin, TNF, TNF-a, TNFA, TNFSF2, Tumor necrosis factor ligand superfamily member 2