(A) Cell death of U-266-1970 cells in the absence (•) or presence (○) of anti-Fas MoAbs (CH-11; 100 ng/mL) or control IgM Abs (100 ng/mL; ▴). U-266-1970 cells were preincubated for 96 hours with IFN-γ in concentrations ranging from 0 to 1,000 U/mL before the addition of anti-Fas MoAbs or isotype-specific control MoAbs and harvested for TUNEL and flow cytometry analysis at 24 hours of incubation. Vertical bars indicate the standard error of mean (SEM). (B) Cell number and viability of U-266-1970 cells incubated with IFN-γ at increasing concentrations (0 to 1,000 U/mL) in the presence of IL-6 (20 U/mL). Cells were harvested at 96 hours and the number of viable cells (•) and the percentage of viability of the total number of cells (○) were determined by using trypan blue exclusion. Vertical bars indicate the SEM.