Effects of repeated administration of granulocyte colony-stimulating factor (G-CSF) on neutrophil counts, plasma cytokine, and cytokine receptor levels.

Granulocyte colony-stimulating factor (G-CSF) induces the release of mature neutrophils from storage pools and stimulates differentiation of myeloid progenitor cells. Recently, it has been shown that a standard dose of G-CSF induces immunophenotypical and functional changes of neutrophils that persist for 1 week. The authors investigated the effects of 300 micrograms of G-CSF administered subcutaneously twice, 1 week apart, to 10 healthy volunteers, on neutrophil and monocyte counts and on the plasma levels of interleukin 1 receptor antagonist (IL-1ra), tumour necrosis factor-alpha (TNF-alpha), soluble TNF receptor (sTNF-r) p55 and p75. G-CSF on both occasions increased neutrophil and monocyte counts and the plasma levels of all cytokines and cytokine receptors measured. All parameters assessed had returned to baseline prior to the second administration of G-CSF. The increases in neutrophil counts and plasma IL-1ra levels were larger following the second injection, whereas the increase in plasma sTNF-r p75 levels was smaller. G-CSF induced increases in monocyte counts, TNF-alpha and sTNF-R p55 levels did not differ between the first and second injection. Our finding of an increased response of healthy humans to a second G-CSF challenge 1 week following a first one may be due to long-lasting increases in storage pool neutrophils.