CMV-specific CD8⁺T cells from CLL patients are as cytotoxic as those from HCs. Enriched CD8⁺ T cells from CLL patients and HCs (effectors) were incubated with DDAO-labeled CMV-peptide–loaded HLA-I–matched EBV-LCLs (targets) at various effector-to-target ratios. After 6 hours of incubation, cell death in the target cells was measured using 3,3′-Dihexyloxacarbocyanine iodide and propidium iodide. As a negative control, enriched CD8⁺ T cells and nonloaded EBV-LCLs with the highest effector-to-target ratio were taken along. Results are presented as the percentage of specific lysis, calculated by subtraction of spontaneous cell death within CMV-peptide–nonloaded EBV-LCLs with mean ± SEM of n = 6 CLL and n = 3 HCs. No significant differences were observed between HCs and CLL at any effector-to-target ratio (Mann-Whitney U test).