Cxcr2 mediates G-CSF–induced mobilization and increased motility of neutrophils in vivo. (A) Time course of mean blood levels ± SEM of Cxcr2-binding chemokines determined by ELISA after systemic application of G-CSF in mice (2 independent experiments with 3 mice per sample point in each experiment). (B) Levels of circulating neutrophils in the blood of Cxcr2^+/+ or Cxr2^−/− mice treated with either PBS or G-CSF. Data represent one experiment with 5 mice per group. (C) Levels of circulating neutrophils in the blood of G-CSF–mobilized mice after pre-injection of Cxcr2 antiserum or control NRS 48 hours previously. Representative fluorescence-activated cell sorting histogram and the spectrum of results from all individual animals analyzed are shown. (D) Velocity and migratory activity of neutrophils in the BM of mice treated with either NRS or anti-Cxcr2 48 hours before injection of G-CSF. Motility values were measured by intravital microscopy 1 hour after injection of G-CSF in 5 independently analyzed animals per group; ns = nonsignificant. In panels B through D, the horizontal bar indicates the mean value. The accompanying video is provided as supplemental Video 5.