Effect of Th1 cytokines on monocyte apoptosis induced by Fas crosslinking or by γ-irradiation. Monocytes (4 × 105 cells/mL) were cultured for 24 hours (in the absence of poly–L-lysine) either in the absence of any stimuli (medium), in the presence of an agonistic antibody to Fas (2 μg/mL), or after γ-irradiation (10 Gy). Addition of the Fas MoAb or γ-irradiation was performed either on monocytes incubated with medium alone (None) or on monocytes that had been preincubated for 1 hour with IL-12 (400 ng/mL) or with IFN-γ (100 IU/mL). Percentages of apoptotic cells were assessed by cytofluorimetry analysis using the nuclear dye acridine orange. These results are representative of three independent experiments, except for the effect of IFN-γ on Fas MoAb-induced apoptosis, which was found to vary (either enhancing or reducing apoptosis) in five different experiments (see Results and Discussion section).
