Portrait of an executioner: the molecular mechanism of FAS/APO-1-induced apoptosis.

Fas/APO-1 is a member of the TNF receptor family and plays a dominant role in the immune system, down-regulating the immune response and contributing to T-cell-mediated cytotoxicity. Activation of Fas/APO-1 by either natural ligand or agonist antibody initiates apoptosis. Until recently, however, the mechanism by which Fas/APO-1 engages the cell death machinery has been an enigma. Here we describe a proposed molecular mechanism by which this cell surface death receptor signals the suicide response.