Model schematic and data sources visualized. (A) Neutrophils exit the marrow reservoir at rate R(t) before disappearing from the blood at rate γ. (B) Splined data of neutrophil responses to exogenous G-CSF IV infusions from Krzyzanski et al17 (Figure 2) and Wang et al18 (Figure 7). (C) Rate of change in neutrophil numbers in the blood calculated from digitized splined data (from Krzyzanski et al17 [Figure 2] and Wang et al18 [Figure 7]), differentiated with respect to time. Note that by 1 day after administration, dN(t)/dt < 0 for each of the 3 sources. (D) Right side of the Inequality 2; the maximal value provides a lower bound for γ.