PAF1 and leukemia: The results showed that both PD1 CAR T cell products controlled leukaemia progression, whereas PD1 CAR19-IL18 demonstrated a slight enhancement; by contrast, PD2 CAR19 was not able to achieve remission during the CAR stress test, while PD2 CAR19-IL18 prevented leukaemia expansion (Fig. 5h,i and Extended Data Fig. 7), demonstrating that 4th-gen CAR design improved on-chip response, especially for those whose 2nd-gen CAR T cell product generated suboptimal anti-leukaemia responses.