Proliferation potential of CD19 CAR T cells. (A) Flow cytometry analysis of CFSE-labeled cells transduced either after IL-7 culture or CD3 activation after stimulation with anti-CD3/CD28–coated beads for 5 days. (B) Proliferation index of CFSE-labeled cells transduced either after IL-7 culture or CD3 activation after stimulation above. Graph depicts each data point from 5 donors with lines connecting data points from an individual donor. Statistics were calculated by 2-tailed Wilcoxon rank sum test. ∗P = .0317. (C) Flow cytometry analysis of depicting fluorescence of cells transduced either after IL-7 culture or CD3 activation after in situ hybridization with a FITC–labeled PNA telomere probe. (D) Mean relative telomere length calculated using Raji cells as the control population. Graph depicts each data point from 5 donors with lines connecting data points from an individual donor. Statistics were calculated by 2-tailed Wilcoxon rank sum test. ∗∗P = .0079. PNA, peptide nucleic acid.