LMP2-specific T-cell recognition of SNK 6 exceeds that of a LCL. Dual-color flow cytometry: the x-axis represents fluorescence from CFSE-stained CD8⁺ effectors, and the y-axis denotes IFN-γ release as determined by intracellular staining. CFSE-negative cells (ie, LCL or SNK 6 targets) have been gated out of this analysis. HLA class I–mismatched LCLs and SNK 6 transduced with a control retrovirus (+ control RV) are negative controls. The top plots within panels A and B indicate T cells expressing IFN-γ in response to endogenously processed peptide, while the bottom plots of each panel show IFN-γ expression by T cells after preincubation of targets with exogenous cognate peptide (+ peptide). Numbers in the right quadrants indicate the percentage of cells positive (top quadrant) or negative (bottom quadrant) for IFN-γ release. (A) SSC-specific CD8⁺ clones tested against HLA-matched LCLs and SNK 6-A11. (B) Effector T cells expressing a recombinant SSC/A11 TCR tested against A11+ LCL and SNK 6-A11.