Figure 1.

Different killing kinetics of target cells showing GrzB versus Casp8 activity. HeLa cells were cotransfected with NES-RIEADS-mCherry (for GrzB), NES-ELQTD-GFP (for Casp8), and CD48. Confocal time-lapse microscopy started immediately after NK92-C1 cell exposure (E/T = 3). From two independent experiments, 52 cells were classified according to strength of RIEADS- and ELQTD-cleavage. Three dying cells showed no (<10%) reporter cleavage and were excluded. (A) Responses of example single cells (upper row, real time) or of cell subpopulations (mean ± SD, time point 0 set to time of cell death) with more Casp8 than GrzB-reporter cleavage (left), equal reporter cleavage (center), or more GrzB- compared with Casp8-reporter cleavage (right), from one experiment (time resolution, 4 min). (B) Time of target cell death (Cell death), time point of NK cell contact with target cell (Cell contact), and the time span (from NK cell contact to target cell death) for the three cell subpopulations of both experiments is shown. ****, P ≤ 0.0001; *, P ≤ 0.05 (unpaired, two-tailed t test with Welch’s correction).