Inhibition of CTL-mediated cytolysis by concanamycin A (CMA) and CTL-mediated activation of caspases. (A) Four PI-9–positive and HLA-A2–positive lymphoma cell lines were preloaded with influenza peptide (♦) or HIV peptide (⋄) and coincubated with an influenza-peptide–specific T-cell line for 4 hours without (solid lines) or with (broken lines) 50 nM CMA. Specific cytolysis was detected by propidium iodide assay. Means and SEM of 3 experiments are shown. (B) Lymphoma cells were preloaded with influenza peptide (♦) or HIV peptide (⋄) and coincubated with an influenza-peptide–specific T-cell line for 2 hours. Specific apoptosis was detected by FITC–VAD-FMK. Means and SEM of 3 experiments are shown. The difference between specific (influenza peptide) and unspecific (HIV peptide) apoptosis for all cell lines is statistically significant (P ≤ .01, Wilcoxon test).