Effector cells derived from naive rather than memory precursors express the genetically engineered TCR with greater frequency. Cryopreserved leukapheresis samples were thawed and rested overnight. CD8⁺ T-cell subsets were isolated then stimulated with allogeneic feeders, anti-CD3, and IL-2. Cells were transduced to express the 1G4-α-95:LY mutant TCR 48 hours after stimulation, and flow cytometric analysis was performed 10-16 days after stimulation. (A) Expression of Vβ13.1 (the 1G4 β-chain clonotype) and binding to HLA-A2-NY-ESO-1_157-165 tetramer by transduced cells from 2 representative patients. Gate frequencies are displayed. (B) Frequency of Vβ13.1⁺ cells following transduction of samples from 9 patients (**P < .001).