TNF-alpha is a homotrimeric 17 kDa protein, that interacts with either one of the two types of TNF-receptors, termed I and II, leading to receptor cross-linking and signal transduction. The receptors differ strongly in their intra-cellular signaling pathways. TNF-alpha was originally described as a highly cytotoxic cytokine for tumor cells, it causes tumor necrosis in vivo and shows cytolytic activity against tumor cells in vitro. Furthermore, TNF-alpha is found to be a central mediator in many inflammatory and immunological processes. It can be induced by various products of micro-organisms and by various cytokines leading to expression of a wide variety of cytokines. The pro-inflammatory properties of TNF-alpha play a central role in several auto-immune diseases such as rheumatoid arthritis and inhibition by neutralizing molecules have been shown to be beneficial in patients.Synonyms: Cachectin, TNF, TNF-a, TNFA, TNFSF2, Tumor necrosis factor ligand superfamily member 2