Neutrophil kinetics shortly after initial administration of recombinant human granulocyte colony-stimulating factor: neutrophil alkaline phosphatase activity as an endogenous marker

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) was administered (1.5 micrograms/kg body weight) subcutaneously once daily for 5 to 9 days to 5 patients with malignant lymphoma. In all patients, initial administration of rhG-CSF induced a rapid fall in the neutrophil count within 30 minutes, followed by a recovery and an increase in the neutrophil count within 150 min. A rapid fall in the neutrophil count was accompanied by increased expression of neutrophil C3bi-receptors, and neutrophils left in the circulation had lower activity of neutrophil alkaline phosphatase (NAP) and phagocytosis. A decrease in the NAP scores observed at 30 min reflected a preferential decrease of neutrophils with high NAP activity. A recovery and an increase in the neutrophil count were accompanied by a further decrease of NAP scores, which was caused by a preferential increase of neutrophils with lower NAP activity. The NAP scores of mature neutrophils from peripheral blood were not affected by in vitro treatment of cells with rhG-CSF for up to 150 min at 37 degrees C. These findings and the previous observations that neutrophils in the circulating and marginal pools have high NAP activity and neutrophils in the bone marrow pool have low NAP activity taken together suggest that, following initial administration of rhG-CSF, functionally active neutrophils leave the bloodstream preferentially, which is primarily followed by an influx of neutrophils from the bone marrow, but not by demargination of sequestered neutrophils.