Evidence for caspase-dependent and ROS-dependent pathways of IVIg-mediated death. The caspase inhibitor z-VAD-fmk blocked IVIg-mediated neutrophil death completely. However, the enhanced IVIg-triggered death after GM-CSF preincubation was only partially blocked by the caspase inhibitor. The ROS scavenger NAC blocked IVIg-mediated death in GM-CSF–primed neutrophils, whereas the inhibitor of ROS production, DPI, completely blocked IVIg-mediated death in the absence and presence of GM-CSF. Results of 20-hour cultures are shown (n = 3). ***P < .001.