Fas knock down in EBV-CTLs increases CTL survival in the presence of cells producing hFasL. (A) The percentage is shown of dead EBV-CTLs transduced with siRNA10, EV, or CsiRNA cocultured (ratio 1:1) with COS-7/hFasL (▦) or COS-7/EV (□). EBV-CTLs transduced with siRNA10 were more resistant to FasL-induced death compared with CsiRNA-transduced CTLs. Data represent the mean ± SD of 4 different donors (^*P = .008). EBV-CTLs were then transduced with GFP-siRNA10 (B) or GFP-CsiRNA (C) and cultured for 4 days with COS-7/EV or COS-7/hFasL (ratio 10:1). A selective increase of GFP⁺ (▦) compared with GFP^- (□) cells was observed in CTLs with knocked down Fas (B) (^**P = .001), while no selection was observed in control CTLs transduced with GFP-CsiRNA. Data represent the mean of 3 different donors.