Neutrophil activation by the TLR2 ligand, zymosan, is enhanced by GM-CSF treatment.

(A) GM-CSF enhances zymosan-stimulated IL-8 secretion from neutrophils but not from monocytes. Neutrophils and monocytes were incubated with or without GM-CSF (1-100 U/mL) and stimulated with (○) zymosan (10 μg/mL) or (▪) medium alone. IL-8 secretion was measured 18 hours later by ELISA. (B) Zymosan stimulates TLR2-expressing cells but not TLR4-expressing cells. HEK293 clones expressing TLR2, TLR4, or no TLR (none) were incubated with (▪) zymosan (10 μg/mL), (░) phenol-extracted LPS (10 ng/mL), or (■) medium alone. Secretion of IL-8 was measured 18 hours later by ELISA.