Magnitude and duration of functional CD19 CAR engraftment. (A) Representative engraftment and detection of CD19 CAR⁺/EGFRt⁺ T cells in peripheral blood (PB), bone marrow (BM), and cerebrospinal fluid (CSF) 21 days after infusion. (B) Representative functional activity of CD19 CAR product as measured by clearance of B cells (leukemic and normal) in PB, BM, and CSF. (C) Magnitude and duration of CAR engraftment by flow cytometric quantitation of EGFRt⁺CD3⁺ T cells. (D) Durability of functional CD19 CAR engraftment in treated patients based on BCA. Flu/cy, fludarabine and cyclophosphamide.