Example of CAR T cell with high calcium responses upon interactions with tumor cells. B cell lymphomas were established by i.v. injection of 0.5 x 106 Eμ-myc-DEVD cells in C57BL/6 mice after sublethal irradiation (4 Gy). 7 d later, mice were injected i.v. with 20 x 106 purified CAR T cells expressing the Twitch2B genetically encoded calcium indicator. Bone marrow intravital imaging was performed 40 h after T cell transfer. The highlighted CAR T cell (white circle) exhibited a first calcium increase after a contact with a tumor cell (without killing) and a second calcium responses (associated with killing; see arrow) upon encountering a new target. Low and high calcium concentrations are shown in yellow and red, respectively. Tumor cells are shown in brown when alive and green when undergoing apoptosis. Scale bar represents 10 μm. Total duration = 37 min.
