In vivo persistence of modified T cells. Genomic DNA was isolated from patient PBMCs collected at serial time points after T-cell infusions and used for quantitative real-time PCR using one primer within the human CD3ζ gene and the other from the adjacent CD4 transmembrane region in the scFvFc:ζ plasmid. The copy number of scFvFc:ζ-specific DNA based on quantitative reverse transcription-PCR results for all treated patients is shown. Arrows denote T-cell infusions, and horizontal black bars indicate the period of subcutaneous IL-2 injections for patients F, G, H, and I. Modified T cells were detectable for 12, 5, 21, 63, 63, 35, and 65 days, respectively, in the 7 patients.