Role of Fas ligand (CD95L) in immune escape: the tumor cell strikes back.

Several different tumor types have recently been shown to express functional Fas ligand (FasL), which may represent an additional mechanism of tumor escape. However, the in vivo significance of these findings in the context of potent adversaries such as activated CTL or NK cells remains to be fully established. The potential interactions between tumor cells and the host immune response are thus more complex than previously thought; their elucidation will benefit the rational design of cancer immunotherapy strategies.