Fig. 3

PD-1 downregulation partially mitigates CAR T cell exhaustion. A Schema of repetitive tumor stimulation assay. RB-340-1 or cRB-340-1 were co-cultured with FaDu tumor cells at Day 0 (E:T  = 1:4) and re-challenged with FaDu cells at day 4, 8 and 12 (indicated by yellow arrows). Non-stimulated CAR T cells were maintained in culture in the presence of 100 U ml⁻¹ IL-2. At indicated time points (red arrow heads), CAR T cells were harvested and analyzed by flow. Surface expression of exhaustion markers CD39, PD-1, TIM-3 and LAG-3 at day 16 for non-stimulated (B) and stimulated CAR T cells (C). D Representative kinetics of PD-1, TIM-3, LAG-3 and CD39 after stimulation with FaDu cells (solid lines) and non-stimulation (dash lines). E Kinetics of CAR T proliferation and IL-2, IFN-γ and TNF-α secretion after stimulation with FaDu cells. p values are indicated by the asterisks in all graphs referring to statistical difference between RB-340-1 and cRB-340-1