Z-VAD-fmk, contrary to Z-DEVD-fmk, inhibits Fas-mediated apoptosis in cytokine-activated TEC. A representative experiment (from 3 independent experiments) is shown. Human TEC were activated for 48 hours with 1 ng/mL IL-1-β, 10 ng/mL TNF-, and 500 U/mL IFN-γ. After two washes, cells were preincubated with 20 μmol/L Z-VAD-fmk or 20 μmol/L Z-DEVD-fmk where indicated, before adding 0.5 μg/mL IgM or 0.5 μg/mL anti-Fas. Twenty-four hours later, cells were harvested and the number of living cells was measured using the Trypan exclusion dye method (A); annexin-V–FITC binding was also measured (B).