Frequency and kinetics of effector apoptosis are dependent on functional activation provided by varying numbers of tumor cells. (A) Box and whisker plots (extremities indicate range) of the distribution of time to AICD of single CAR⁺ T cells after target cell killing. (B) Donor variation in the average frequencies of apoptotic killer CAR⁺ T cells. P-values were computed using an unpaired two-tailed t-test (n=4).