Tumor necrosis factor alpha (TNF-α), also known as cachectin and TNFSF1A,  is an adipokine involved in systemic inflammation and is a member of a group of cytokines that stimulate the acute phase reaction. It is produced chiefly by activated macrophages, although it can be produced by many other cell types such as CD4 lymphocytes, NK cells, neutrophils, mast cells, eosinophils, and neurons. It functions as a multipotent modulator of immune response and further acts as a potent pyrogen. TNF-α circulates throughout the body responding to stimuli (infectious agents or tissue injury), activating neutrophils, altering the properties of vascular endothelial cells, regulating metabolic activities of other tissues, as well as exhibiting tumoricidal activity by inducing localized blood clotting.
TNF-α may play a significant role in the pathogenesis of inflammatory disease of the joints and other tissues. Recently, a growing body of information has pointed to a role for TNF-α in the pathogenesis of AIDS. Measurement of TNF-α levels has also been shown to be useful in transplant research.