Tumor necrosis factor is a cytokine involved in systemic inflammation and is a member of a group of cytokines that all stimulate the acute phase reaction. TNF is mainly secreted by macrophages. TNF causes apoptotic cell death, cellular proliferation, differentiation, inflammation, tumorigenesis and viral replication, TNF is also involved in lipid metabolism, and coagulation. TNF's primary role is in the regulation of immune cells. Dysregulation and, in particular, overproduction of TNF have been implicated in a variety of human diseases- autoimmune diseases, insulin resistance, and cancer. Tumor Necrosis Factor-a human recombinant produced in E. coli is a single, non-glycosylated, polypeptide chain containing 158 amino acids (157 amino acids of the mature human TNF-alpha and an N-terminal methionine) and having a molecular mass of 17.5 kDa. TNF-alpha is purified by standard chromatographic techniques.