Mean (± SEM) G-CSF (A), TNF (B), IL-6 (C), and IL-8 (D) concentrations after endotoxin administration (4 ng/kg) in humans. Placebo (○) or G-CSF (5 μg/kg; •) was administered 2 hours before endotoxin challenge (group 1) or 24 hours before endotoxin administration (group 2).