Effects of protease inhibitors on apoptosis. (A) Comparison of the ICE antagonist zVADfmk with the serine protease antagonist TPCK. Cells were incubated for 48 hours in the absence or presence of 10 μmol/L methylprednisolone or 10 μmol/L fludarabine with or without 25 μmol/L zVADfmk or 25 μmol/L TPCK, and the percentage of hypodiploid cells was determined by PI staining and FACS analysis as outlined in Materials and Methods. Results from two representative experiments (patients 6 and 21 in Table 1) (□, experiment 1, ▪, experiment 2). (B) Effects of the peptide antagonist zAPFcmk. Cells were incubated as described above with or without 25 μmol/L zAPFcmk, and the percentage hypodiploid cells was determined by PI staining. Results from three representative experiments (patients 8, 11, and 9 in Table 1) (□, experiment 1; ▪, experiment 2; ▧, experiment 3). (C) Effects of TLCK. Cells were incubated for 48 hours in the absence or presence of 10 mmol/L methylprednisolone with or without 50 mmol/L TLCK, and the percentage of hypodiploid cells was determined by PI staining and FACS analysis. Results from four representative patients (5, 6, 7, and 20 in Table 1) (□, patient 5; ▪, patient 6; (▧), patient 7; (▧), patient 20).