CD19 and leukemia: As for the persistence, dynamic FCM analysis showed that CAR T cells in PB persisted for ≤20 days and the percentage of CD19 CAR T cells of total lymphocytes decreased rapidly in most of the isolated EM‐ALL patients (Figure 1A, usually more rapidly than those with leukemia blasts in BM or PB or both based on our other studies, in the paper).