IL13 and leukemia: Intriguingly, cytokine profiling from on-chip tests demonstrated that 4-1BBζ-CAR secreted more IL-13 (a Th2 cytokine), and CD28ζ-CAR and ICOSζ-CAR secreted more IL-10, whereas this is not the case for 2D tests with respective co-cultures of CAR T cell and leukemia blast (Extended Data Fig. 10c–e and Fig. S11).