Effect of SB 290157 is C3a-C3aR axis-dependent. Wt C57Bl/6 (C3^+/+), C3^–/– C57Bl/6, BALB/c C3aR^–/–, and wt BALB/c (C3aR^+/+) mice were mobilized for 3 days with G-CSF (250 μg/kg subcutaneously/day) (n = 12 animals/group). SB 290157 (500 μg/mouse) was injected intraperitoneally with the last dose of G-CSF. (A) The number of circulating CFU-GMs/50 μL PB in C57Bl/6 wt and C3^–/– mice with or without SB 290157. (B) The number of circulating CFU-GMs/50 μL PB in BALB/c wt and C3aR^–/– mice with or without SB 290157. *P < .000 01 compared with wt mice mobilized with G-CSF alone. Data are expressed as mean ± standard deviation.