Fig. 3

FLT3L CAR-T cells showed specific cytotoxic ability against FLT3 positive primary AML. a FLT3 surface expression on patients’ AML cells (44~ 95% blast count; patients 1 to 5, FLT3-ITD; patients 6 to 10, FLT3 wild type) was investigated by flow cytometry. Black line, anti-FLT3; gray line, isotype control. SFI of FLT3 staining was calculated by dividing median fluorescence obtained with the FLT3 mAb by median fluorescence obtained with the mouse IgG1 κ isotype control. The red dotted line represented SFI 1.4 as a defined threshold for FLT3 positivity. b Cytotoxic activity of FLT3L CAR-T against FLT3-ITD (bold line) or FLT3-WT (dotted line) primary AML cells. Target cells and effector cells were co-cultured for 48 h at the indicated E:T ratio of 1:4. Anti-CD33 antibody and anti-CD3 antibody were used to recognize different cell types. c Percentage of CD3⁺CD107a⁺ T cells after being co-cultured with FLT3-ITD (bold line) or FLT3-WT (dotted line) primary AML cells for 5 h was determined by flow cytometry. d CAR-T or VEC-T cells were co-cultured with primary AML cells for 48 h. IFN-γ, TNF-α, and IL-2 amounts in the supernatants were detected by using ELISA