Tumor necrosis factor: recent advances.

Tumor necrosis factor is a protein secreted by activated monocytes. In addition to its known cytotoxic or cytostatic effect on some tumor cells, recently it was discovered to have multiple effects on normal cells. These effects include modulation of cell growth and function, production of growth factors, and induction of surface antigens. In this article we review some of the advances which were made since the gene for tumor necrosis factor was cloned.