Antileukemia cytotoxicity is mediated by CD8⁺ cells and involves the secretory pathway (perforin/granzyme) rather than the FAS/FAS-L pathway. Cytotoxicity is represented as the percentage of specific lysis. Blocking antibodies (anti–LFA-3, anti–ICAM-1, anti-MHC I, and anti-Fas) were used at 10 mg/mL. CD8 depletion was performed by magnetic bead depletion and the depleted population was greater than 97% CD4⁺ T cells. Brefeldin A was used at 5 mg/mL. This experiment was performed using leukemia cells and CTL from ALL-17 and is representative of four independent experiments (4 different patients).