Fold expansion in total cells, CFU-Fs, and CFU-Os as a function of cytokine combination and the effect of cytokine combination on total cell, CFU-F, and CFU-O expansion. (A) The fold expansions in total cell, CFU-Fs, and CFU-Os on day 21 were calculated relative to the day 0 values of each 24 cytokine combination. Statistical analysis was performed using the Student t test between the no cytokine and SCF plus IL-3 treatment conditions and between the SCF plus IL-3 and SCF plus IL-3 plus PDGF treatment conditions. Statistical differences (P < .05) were observed in total cell, CFU-F, and CFU-O expansion between the no cytokine and SCF plus IL-3 groups (denoted by the asterisk) and between the no cytokine and SCF plus IL-3 plus PDGF treatment groups (denoted by double asterisks). No C indicates no cytokine; F, FGF; P, PDGF; I, IL-3, and S, SCF. Each bar represents the mean ± SD (n = 3, performed in triplicate). Panels ii-iv show the fold expansion in total cells, CFU-Fs, and CFU-Os as a function of time in the no cytokine, SCF, IL-3, and SCF plus IL-3 conditions. (B) Graphic display of the effects (β) of SCF, IL-3, PDGF, and FGF and their 24 combinations on total cell, CFU-F, and CFU-O expansion. Bars to the left of the center axis in each graph represent negative β values, whereas positive β values are represented on the right. Statistical significance is denoted by the asterisk (P < .05).