Neutrophil activation by commercial LPS is enhanced by GM-CSF treatment.

(A) GM-CSF enhances commercial LPS-stimulated IL-8 secretion from neutrophils but only weakly enhances neutrophil responsiveness to phenol-extracted LPS. Neutrophils and monocytes were incubated with or without GM-CSF (1-100 U/mL) and stimulated with (○) commercial (stock) LPS (10 ng/mL), (●) phenol-extracted LPS (10 ng/mL), or (▪) medium alone. IL-8 secretion was measured 18 hours later by ELISA. (B) Commercial (stock) LPS stimulates both TLR2-expressing cells and TLR4-expressing cells, but phenol-extracted LPS stimulates only TLR4-expressing cells. HEK293 clones expressing TLR2, TLR4, or no TLR (none) were incubated with (░) commercial (stock) LPS (10 ng/mL), (▪) phenol-extracted LPS (10 ng/mL), or (■) medium alone. Secretion of IL-8 was measured 18 hours later by ELISA.