TCR cell-surface composition independent of whether the TCRs are retrovirally or endogenously expressed. Sorted CMV-TCR–transferred T-cell lines or mock-transduced T-cell lines (> 98% GFP⁺NGFR⁺) derived from 2 different healthy persons (A) and (B) were tested for cytolytic activity against HLA-A2⁺ EBV-LCLs loaded with 1 μM CMV peptide (black bars) or nonpeptide-loaded EBV-LCLs in a 4-hour cytotoxicity assay. The cytolytic activity against nonpeptide-loaded target cells was for all transduced T-cell lines less than 10%. All the transduced T-cell lines tested originated from wells that were seeded with 25 double marker gene–positive T cells. (C) The percentage of CMV^A2 tetramer–positive CMV-TCR–transduced T cells is plotted against the cytolytic activity of the T cells toward HLA-A2⁺ EBV-LCLs loaded with 1 μM CMV peptide. Labeling with PE-conjugated CMV^A2 tetramers was performed for 2 hours at 4°C. Our results show that the cytolytic activity of the T-cell lines is correlated with the percentage of tetramer-positive cells in these cultures (P > .7).