Human TEC were previously activated for 48 hours with 1 ng/mL IL-1-β, 10 ng/mL TNF-α, and 500 U/mL IFN-γ. After 7 hours of incubation with 0.5 μg/mL anti-Fas CH-11 antibody or mouse IgM, TEC were harvested and annexin-V–FITC binding (among living cells) was measured. Remaining cells were lysed and DEVDase activity was evaluated using a colorimetric substrate. The activity index is the ratio between DEVDase activity in the presence of agonistic anti-Fas antibody and DEVDase activity in control conditions. Results are from two independent experiments. In comparison, in a granule-mediated apoptosis in which caspase-3 family was clearly involved,36 DEVDase activity quantified in the same experiment was increased 12.1 and 15.6 times, respectively, in K562 target cells killed by lymphokine-activated killer cells compared with K562 alone.