Changes in the number of total CFCs in the PB during the administration of FL at 20 μg/kg (□), G-CSF at 250 μg/kg (), and FL plus G-CSF () for 5 days. Data are mean ± SE and are expressed as fold increases relative to mice before treatment. Points that differ significantly from data for G-CSF administration on the same day are marked: **P < .005, *P < .05.