Death-inducing functions of ligands of the tumor necrosis factor family: a Sanhedrin verdict.

Members of the tumor necrosis factor ligand family can kill cells in a rather straightforward manner. They induce their receptors to recruit and activate caspases, enzymes that are critically involved in the death process, and this activation is further amplified by intracellular mitochondria-associated mechanisms. The potentially hazardous expression of the ligands occurs widely in the body; it is antigen-restricted only in the lymphocytes. Yet, in addition to control modes affecting ligand expression, there are numerous inhibitory mechanisms that act within target cells, to make doubly sure of avoiding an undue 'death verdict', while allowing the cells to exhibit other, noncytocidal effects of the ligands.