TNF-α is the prototype cytokine of the family of TNF-related ligands, which are based on structural and functional homologies. TNF-α is synthesized as type II transmembrane protein. TNF-α can be recognized by two different membrane receptors, namely TNF-R1 and TNF-R2. TNF-α is present in a membrane-bound (tmTNF) as well as soluble form (sTNF). The membrane-bound form of TNF-α is recognized by both TNF receptors with high affinity, whereas the soluble form is recognized more superiorly by TNF-R1. TNF-α is produced by many different cell types including macrophages, T lymphocytes, NK cells, neutrophils and endothelial cells. Cells differ in the expression of the two TNF-receptors and sTNF versus tmTNF, respectively. TNF-α, a homotrimeric 17 kDa protein, is a potent mediator of inflammatory and metabolic functions. TNF-α 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. Furthermore, TNF-α has been implied as central mediator in shock induced by gram negative micro-organisms. TNF-α induces on its turn the production of many other cytokines. Furthermore, TNF-α has been found in inflammatory foci such as synovial effusions in rheumatoid arthritis, systemic circulation in septic shock, parasitemia and rejection of renal transplants.Synonyms: Cachectin, TNF, TNF-a, TNFA, TNFSF2, Tumor necrosis factor ligand superfamily member 2