Stimulatory effect of cytokines on the in vitro migration of BM and PB CD34⁺ cells. The concentrations of TNF-, GM-CSF, IL-6, G-CSF, IL-3, and SCF and the calculations for the percentage of stimulation are described in Materials and Methods. Bar graphs represent the mean percentage of stimulation relative to the control, which is set at the baseline value of 0%, ± standard deviation from duplicate experiments. *Significant difference in the effect of TNF- and G-CSF on migration of BM versus PB CD34⁺ cells (P = .015 and .004, respectively).