Potent induction of apoptosis in CD7-negative bystander tumor cells. Mixed cultures of Ramos.CD7 target cells and Raji bystander cells (ratio 1:1) were treated for 16 hours with scFvCD7:sFasL (100 ng/mL) in the presence or absence of mAb TH69 or mAb Alf2.1. The differential fluorescent labeling of target and bystander cell populations was used to separately evaluate apoptosis induction by ΔΨ in Ramos.CD7 target cells (A) and Raji bystander cells (B). Indicated values are mean + SEM of 3 independent experiments. Statistical analysis was performed using 2-tailed Student t test. ^*P < .05; ^**P < .01.