In germ-free mice the IL-8–induced mobilization is significantly reduced. There were 3 groups of OF1 mice mobilized with a single intraperitoneal injection of 30 μg IL-8 or saline: normal controls (saline: n = 3, IL-8: n = 7), mice that had been treated with ciprofloxacin and polymyxin B for 1 week (saline: n = 3, IL-8: n = 7), and germ-free OF1 mice (saline: n = 3, IL-8: n = 7) not treated with antibiotics. At 20 minutes after the IL-8 injection, the mice were killed and blood was harvested. Results are expressed as means ± SD. *P < .05 compared with the controls.