CAR-FACS analysis measures CAR19 expansion across histologic subtypes over 7 orders of magnitude. (A-B) PFS and OS curves in Stanford’s CAR19 cohort for LBCL, FL, and MCL are representative of published results. Dotted lines represent respective median time to event. Only the first 30 months of follow-up are illustrated. (C) Percent and absolute plots of longitudinal CAR19 expansion in the first month demonstrates CAR19s expand over 7 orders of magnitude with CD8 dominance. Dotted lines represent theoretical limits of detection based on prior assay calibration. (D) Absolute CD4 and CD8 CAR19 counts are highly correlated during expansion. (E) There is a small relative increase in CD8 CAR19 expansion at D14 and D21 with increasing persistence of the CD4 CAR19 at D28 (Wilcoxon test). ∗P < .05, ∗∗P < .01.