In vivo persistence of modified T cells. (A) Persistence of 19-28z⁺ T cells after infusion in the peripheral blood. CD3⁺ T cells derived from the peripheral blood samples of patients with CLL and ALL at various time points after infusion were activated with Dynabeads. Quantitative PCR analysis was performed, and the average vector copy number (vcn) was determined per 100 cells. The average vcn was below the limit of detection for CLL-2 and CLL-3 patient samples at all available data points and, therefore, are not represented. Samples for ALL-1 were not available on day 0 (at 1 hour after infusion). (B) Expression of 19-28z⁺ CAR after infusion after restimulation with either AAPCs or Dynabeads. CD3⁺ T cells derived from ALL-1 peripheral blood 2 days (d2) and 8 days (d8) after infusion were selected and activated with either Dynabeads (top) or AAPCs (bottom). CD3⁺ T cells derived from CLL-8 peripheral blood 5 weeks (wk 5) after infusion were selected and activated with Dynabeads. Flow cytometric analysis was performed with anti-CD3 and anti-CAR Abs 7 days after restimulation. (C) Inverse correlation between peripheral CD19⁺ cell counts and maximum vcn detected in the peripheral blood. The peripheral blood CD19⁺ cell count (obtained by CD19 FACS analysis) is plotted on the x-axis (Table 1). The maximum vector copy number per 100 cells and normalized per 10⁸ infused 19-28z⁺ T cells detected in the peripheral blood after infusion (day 1-8), as shown in panel A, are reported on the y-axis (supplemental Table 2).