Flow cytometric analysis of Fas-induced cell death and colorimetric analysis of Fas-induced caspase-8 catalytic activity in caspase-8L–transfected Jurkat cells.

(A,B) Empty vector– or caspase-8L–transfected Jurkat cells and wild-type Jurkat cells were untreated or treated with 0.5 μg/mL mouse anti–human Fas monoclonal antibody (clone CH11, MBL) for 12 hours. After Fas stimulation, the cells were stained with 40 μg/mL propidium iodide, and the percentage of propidium iodide–positive (dead) and –negative (live) cells was determined by FACScan. Fluorescence-activated cell sorter profiles of empty vector– or caspase-8L–transfected Jurkat cells and wild-type Jurkat cells without or with Fas stimulation are shown in panel A. The presented data are representative of experiments using 3 independent clones of each transformant. The percentage of cell death in vector- or caspase-8L–transfected cells is shown in panel B. The data are from experiments using 3 independent clones of each transformant and represent mean ± SD. (C) Colorimetric analysis of caspase-8 catalytic activity. Either empty vector– or caspase-8L–transfected Jurkat cells were left untreated or treated with 0.5 μg/mL mouse anti–human Fas monoclonal antibody for 4 hours, and the caspase-8 catalytic activity was examined by measuring pNA release as described. All data are from experiments using 3 independent clones of each transformant and represent the mean ± SD.