GM-CSF enhances superoxide generation from neutrophils stimulated with TLR2 ligands.

Neutrophils were pretreated with (▪) GM-CSF or (■) medium alone for 90 minutes and stimulated with zymosan, araLAM, peptidoglycan, or LPS as described in “Materials and methods.” Superoxide generation was determined by a SOD inhibitable cytochrome c reduction assay of cells incubated with cytochrome c, f-MLP, and cytochalasin B for 15 minutes. The mean and SD of 3 replicate determinations are shown. **t test, P < .005 for comparison of untreated versus GM-CSF–treated cells stimulated with zymosan, araLAM, peptidoglycan, or commercial (stock) LPS (which contains a contaminating TLR2 ligand). t test,P = .13 (not significant) for comparison of untreated versus GM-CSF–treated cells stimulated with phenol-extracted LPS (which retains TLR4-stimulating activity, but from which the TLR2 activity has been removed).