Fig. 1

a CD99 recognizing ability of three anti-CD99 mAbs (12E7, 1021527 and 3B2/TA8) in normal blood cells and leukemia cell lines (Jurkat and MOLT-4) by flow cytometry. b Binding kinetics of anti-CD99 scFv with CD99 protein. Analysis of the interaction between the 12E7 scFv and CD99 protein using BLItz biolayer interferometry. c The 12E7 antibody and the anti-CD99 scFv from 12E7 showed a strong correlation in different cell lines based on MFI analysis. d Schematic illustration of the anti-CD99 CAR construct. e Expansion fold change of total T cells transduced with CD19 CAR or CD99 CAR for 14 days. f Percentage of CAR positive cells measured by flow cytometry using Strep-Tag II antibody during the CAR T cells in vitro culture. g Expression of CD99 in normal T cells activated by CD3/CD28 beads. h Cytotoxic activity of anti-CD99 CAR T cells against normal T cells which activated by CD3/CD28 beads in different days determined by calcein release assay at the ratios of 25:1 after 2-3 h co-culture. i Expression of CD99 in CAR positive cells by flow cytometry. j Expansion fold change of CAR positive cells for 12 days. k In vitro cytotoxic activity of anti-CD99 CAR T cells against different normal blood cells. l and m Cytotoxic activity of anti-CD99 CAR T cells against T-ALL cell lines (Jurkat/ CUTLL-1) and T-ALL patients’ blasts (Patient #1/ Patient #2/ Patient #3/ Patient #4) as determined by calcein release assay at different E:T ratios (5:1,25:1) after 2-3 h co-culture. IgG as the negative control.***p ≤ 0.001,**p ≤ 0.01,NS = no significant