Tumor necrosis factor alpha (TNF-alpha), also called cachectin, consists of 157 amino acids. TNF-alpha is a 17.5 kD factor produced by neutrophils, CD4+ T cells, macrophage, NK cells, LAK cells, astrocytes endothelial cells, and smooth muscle cells. TNF-alpha is cytolytic and plays an important role in immune regulation including hemorrhagic tumor necrosis/cytotoxicity and inflammation, and in regulation of antiviral and immune proliferative and activation responses. The active form of this protein is a trimer. Recombinant human TNF-alpha was expressed in E. coli and purified by using conventional chromatography techniques. Additional amino acid, methionine, was attached at N-terminus of the protein.