Tumor Necrosis Factor (TNF) was originally discovered in sera of animals and was found to cause hemorrhagic necrosis of some transplantable mouse and human tumors and to exhibit primarily cytotoxic activities against tumor but not normal cells in vitro. The TNF family consists of two proteins designated TNFα, also called cachectin, and TNFβ, also called lymphotoxin, which are pleiotropic cytokines that can mediate a wide variety of biological effects.