Response of VCAM-1^Δ/Δ animals and controls to treatments by single or combinations of mobilizing agents. (A) Controls or VCAM-1–ablated mice were treated with cyclophosphamide ([CY]; single dose and tested at day 8 after cyclophosphamide), G-CSF alone (G-5d), Flt-3 ligand alone (FL-7d), or G-CSF+FL (G+FL-7d) and evaluated at the end of treatments. BM values refer to calculated CFU-C content of total bone marrow on the basis of measured femur content and its contribution to total bone marrow.⁵¹ PB refers to total circulating CFU-Cs, assuming a blood volume of 2 mL, and spleen CFU-Cs are based on splenic cellularity. The large asterisk indicates P < .05 between f/f and Δ/Δ mice. Note that in the single treatments (G-CSF, FL, CY) circulating PB CFU-Cs were much higher in the ablated group. There was a trend for lower spleen values in ablated mice in all treatments, but statistical significance was seen only in G-CSF (5-day) treatments. A significant proliferative response in BM was seen in both sets of animals with FL treatments and less so in other treatments, but there were no significant differences between the 2 groups. (B) The kinetics of circulating CFU-C disappearance following cessation of G-CSF treatment were studied in one experiment and found to be similar between VCAM-1^f/f and VCAM-1^Δ/Δ mice. Error bars indicate SEM.