CD19 and neoplasm: CAR‐ap9s‐sgc8 or CAR‐ap18s‐sgc8 was cocultured with CAR19‐T cells and CD19‐KO‐Nalm6 or CD19‐KO‐697 cells, followed by apoptosis/necrosis assays using flow cytometry to investigate whether CAR‐bc‐ap overcomes the immune escape of tumor cells from CAR‐T killing owing to antigen loss.