Hematologic response to GM-CSF dose-escalation in vivo. Three patients with acquired PAP who had failed to manifest any significant degree of neutrophilia in response to prolonged administration of 5.0 μg/kg/d of GM-CSF received incrementally increasing single doses of GM-CSF: 7.5, 10.0, 15.0, 20.0, and 30.0 μg/kg. Dose-escalation ceased once the patient had manifest a hematologic response (prospectively defined as ≥1.5-fold increase in neutrophil counts over baseline), and peripheral blood counts were assessed at the time points shown. The kinetics of peripheral blood neutrophil counts are plotted for the first dose, which induced such a hematologic response. Patient no. 6 received yeast-derived GM-CSF, whereas patients no. 5 and 7 received bacterially synthesized GM-CSF.