CD19 and acute lymphoblastic leukemia: Recently, in the study by Hamieh et al. (35), the researchers marked CD19 of ALL cells using fluorescence marking technology, cocultured ALL cells with CAR T-cells (19-BBζ) in vitro, and observed decreased CD19 expression in tumor cells concurrent with a large number of CAR T-cells showed positive CD19 staining, and the transfer of CD19 protein from ALL cells to T-cells showed a characteristic of CAR-mediated trogocytosis.