Effect of ECP on cytokine profile of CAR-T cells. (A) Schematic diagram of beads–based cytokine analysis. After ECP treatment, CAR-T cells or CAR-T cells with auto-PBMCs were stimulated with CD19⁺ tumor cells in the absence or presence of APCs. The supernatants were collected after 4 hour, 24 hour, and 48 hour stimulation. Setting i: stimulation of CAR-T cells without APCs in the ND model. Setting ii: stimulation of CAR-T cells with APCs in the ND model. Setting iii: stimulation of CAR-T cells without APCs in the dilution model. Setting iv: stimulation of CAR-T cells with APCs in the dilution model. (B) The relative change of 24 hour cytokine secretion in the setting i. Every dot represents an individual donor. (C) The relative change of 24 hour cytokine secretion in the setting iv. Every bar represents an individual donor. Relative change of cytokine secretion was calculated = (cytokine concentration of ECP-treated CAR T-cell group – cytokine concentration of ECP-untreated CAR T-cell group)/(cytokine concentration of ECP-untreated CAR T-cell group). (D) Effect of ECP on the dynamics of IL-2 secretion over time. Samples of 3 individual donors were tested. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. APC, antigen presenting cell.