Priming of fMLP-stimulated H₂O₂production by GM-CSF and G-CSF is significantly decreased in neutrophils from MDS patients compared with healthy subjects.

Neutrophils were stimulated for 30 minutes with 1 μM fMLP with or without preincubation for 15 minutes with 5 ng/mL GM-CSF, 2.5 ng/mL G-CSF, or both. The production of H₂O₂ after stimulation was measured by FACS analysis and expressed as a percentage of the fluorescence in unstimulated cells. (A) Mean ROS production was calculated for 8 healthy subjects and 8 MDS patients. Asterisks represent significant differences in percentage H₂O₂ production in the primed groups versus the groups that were stimulated with fMLP alone (P < .05). (B) Respiratory burst-enhancing capabilities of GM-CSF, G-CSF, or both were calculated for each donor as follows: (GM-CSF + fMLP)/fMLP, (G-CSF + fMLP)/fMLP, and (GM-CSF + G-CSF + fMLP)/fMLP. The mean priming capacity of GM-CSF, G-CSF, or both on neutrophil respiratory burst is shown for 8 healthy subjects and 8 MDS patients. Differences between MDS patients and healthy controls were calculated using the Wilcoxon nonparametric tests (*P < .05).