Naive and memory phenotypes are preserved after cytokine stimulation and LV-mediated transduction. PBMCs were cultured in vitro as described and tested for the coexpression of CD45RA/CD27/ΔLNGFr. Percentage of naive (CD45RA⁺/CD27⁺) and memory (CD45RA^–) cells was determined on ΔLNGFr⁺ cells by flow cytometry 96 hours after transduction.