(A) Cell death in the absence (•) or presence (○) of anti-Fas antibodies (CH-11; 100 ng/mL) or control IgM (100 ng/mL; ▴) for 24 hours in U-266-1970 cells preincubated for 96 hours with IFN- in concentrations ranging from 0 to 1,000 U/mL. Cells were harvested and subjected to TUNEL and flow cytometry analysis. Vertical bars indicate the SEM. (B) Cell number and viability of U-266-1970 cells incubated with IFN- 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 (○) was determined by using trypan blue exclusion. Vertical bars indicate the SEM.