FASLG and neoplasm: Most importantly, mouse tumor cells expressing low levels of immunogenic peptide were preferentially lysed by FasL-mediated killing, whereas at higher peptide concentrations, the preference in effector pathway usage was lost and killing was achieved by cooperate action of FasL and PRF (36), indicating that at low concentrations of antigen, only FasL is mobilized whereas at high antigen-density, all granules are released.