Specific killing of EBV⁺ malignant NK and T cells by polyclonal CTLs, containing LMP2-specificities, from ENKTL patients. (A) Dual-color flow cytometry of CTLs derived from 2 ENKTL patients prepared by ex vivo stimulation with LMP2/LMP1 transfected antigen-presenting cells. CTLs were stained with a PerCP (peridinin-chlorophyll protein)–conjugated anti-CD8 antibody and with the phycoerythrin-conjugated HLA-peptide pentamers: HLA-A*0201-CLGGLLTMV, HLA-A*0201-FLYALALLL, HLA-A24-TYGPVFMSL as previously described.⁵  Numbers within the top right quadrant of each plot indicate the percentage of viable peptide/pentamer-specific CD8⁺ cells. (B) The CTLs shown in panel A were tested in standard ⁵¹Chromium-release assays for their ability to kill EBV⁺ NK- and T-cell tumor lines. Results are expressed as the mean percentage of specific chromium release from the target cells at effector:target ratios titrated from 5:1 to 40:1, tested in triplicate. Autologous and HLA-mismatched LCLs were positive and negative controls, respectively, for each assay.