Fas- and perforin-independent mechanism of cytotoxic T lymphocyte.

Cytotoxic T lymphocytes (CTLs) play an important role in elimination of virus-infected cells (1). Recent studies revealed at least two distinct mechanisms that CTLs utilize to destroy their target cells. Both mechanisms induce target cell apoptosis specifically and directionally, but these processes are totally different. One is pore formation on target cell membrane by perforin secreted from CTLs (perforin-granzyme pathway), and the other is ligation of Fas, which is expressed on the surface of target cells and Fas ligand, on the surface of CTLs (Fas-FasL pathway) (2). Here we review our work and describe CTL clones that have novel lytic mechanisms derived from CD4-CD8- lymph node cells of gld mice.