TNF alpha is a cytokine involved in systemic inflammation and is a member of a group of cytokines that stimulate the acute phase reaction. It is produced by activated macrophages, CD4+ lymphocytes, NK cells, and neurons. TNF alpha causes cytolysis or cytostasis of certain transformed cells, being synergistic with interferon gamma in its cytotoxicity. It appears to be directly toxic to vascular endothelial cells. Currently TNF alpha is being evaluated in treatment of certain cancers and AIDS Related Complex.