Effect of anti–TRAIL-R1 and anti–TRAIL-R2 neutralizing antibodies on MEG-01 apoptosis-induced by supernatants harvested from IFNα-treated leukocytes. MEG-01 cells were pretreated for 30 minutes with anti–TRAIL-R1 or anti–TRAIL-R2 neutralizing antibodies (5 μg/mL for each one) before addition of conditioned medium prepared from resting and IFNα-stimulated monocytes and neutrophils or 20 ng/mL rhsTRAIL. Apoptosis rate of MEG-01 cells was then assessed after a 2-day culture. Means ± SEM of the percentage of apoptotic inhibition exerted by anti–TRAIL-R1 or anti–TRAIL-R2 neutralizing antibodies calculated from 3 to 5 independent experiments are shown.