Granzyme B delivery and caspase 3/7 activation are detected during redirected NK killing. Human NK cell lines activate caspase 3/7 and granzyme B biosensors in P815 tumor target cells during redirected killing, as a model for ADCC. P815 cells expressing GLS.DEVD and GLS.VGPD were preincubated with anti-CD16 antibody or isotype control for 30 minutes at 37°C before incubation with NK effector cells at 1:1 (20 000 target cells/well). Cells were spun into contact and RLU was measured in a luminometer set at 37°C every 3 minutes for 240 minutes; every 6 minutes is plotted for clarity. Each datum point represents the mean of 4 replicate wells. Shown is a representative figure from 3 independent experiments using 2 effector cells lines: (A) NKL cells, and (B) KHYG1 cells.