161533 TriKE–treated NK cells overcome MDSC-induced immune suppression. (A) Purified HD-NK cells (n = 6) were cocultured with autologous monocytes or MDSCs for 5 days in the presence of IL-15 (equal molar concentration to the IL-15 in TriKE [50 nM], BiKE [50 nM], or TriKE [50 nM]. HL60 target cells were added 6 hours before staining and assessed for NK cell degranulation (CD107a), IFN-γ production, and proliferation (Ki67). Data are shown as mean ± SEM and statistical analyses were performed using paired Student t test. (B-C) NK cells (n = 4) were added at a 3:1 ratio onto red fluorescent CellTracker-labeled HL60 (B) and MV-4-11 (C) targets and then analyzed for tumor cell killing monitored by hourly fluorescence imaging over 48 hours using an IncuCyte Live Cell Analysis System. Percent killing was quantified using IncuCyte Zoom software (Essen BioScience) and normalized to the number of cells death in the target cell only control group. Statistical analyses of the slopes over time were assessed using a 2-way ANOVA. NS, not significant.