Description
Cytotoxic T lymphocyte (CTL)-mediated cytotoxicity constitutes an importantcomponent of specific effector mechanisms in immuno-surveillance againstvirus-infected or transformed cells. Two mechanisms appear to account forthis activity, one of which is the perforin-based process. Independently, aFAS-based mechanism involves the transducing molecule FAS (also designated Apo-1) and its ligand (FAS-L). The human FAS protein is a cell surfaceglycoprotein that belongs to a family of receptors that includes CD40, nervegrowth factor receptors and tumor necrosis factor receptors. The FAS antigen is expressed on a broad range of lymphoid cell lines, certain of whichundergo apoptosis in response to treatment with antibody to FAS. Thesefindings strongly imply that targeted cell death is potentially mediated by the intercellular interactions of FAS with its ligand or effectors, and that FASmay be critically involved in CTL-mediated cytotoxicity