Allogeneic CTL-mediated apoptosis of resting and CD40-activated CLL B cells.

(A) Fluorescence of PKH26/DiOC₆–labeled target cells incubated with allogeneic effector T cells. CTL effectors were generated from normal human T cells and harvested for the CTL assay. Allogeneic CLL B target cells were mock or were CD40-stimulated for 48 hours, labeled with PKH26 to distinguish targets from effectors, and incubated with effectors at various E/T ratios for 4 hours. Cells were then stained with DiOC₆ for 15 minutes prior to analysis by flow cytometry. DiOC₆^dull or apoptotic cells are represented by the area under each curve on the left side of each histogram. Data are from 1 experiment of 5 CTL assays. (B) The summary of CTL data from 5 separate experiments (mean plus or minus SD).