IN-VIVO ADMINISTRATION OF GRANULOCYTE-COLONY-STIMULATING FACTOR PROMOTES NEUTROPHIL SURVIVAL IN-VITRO

We recently showed that recombinant human granulocyte-colony stimulati ng factor (rhG-CSF) maintained the viability of human neutrophils in i ncubation for up to 72 hours. However, it is not known whether rhG-CSF can enhance neutrophil survival in in vivo situations. To clarify thi s issue, we investigated neutrophil survival in vitro following in viv o injection of rhG-CSF. Neutrophils were obtained from 4 pediatric pat ients with malignancies and healthy adult volunteers before and after rhG-CSF administration. Neutrophils obtained before rhG-CSF treatment started to undergo apoptosis after 24 h of incubation. In contrast, th e survival of neutrophils drawn after rhG-CSF administration increased by approximately 24 h. Concomitantly, the appearance of typical ladde r-like DNA fragmentation was delayed. Such an increase in neutrophil s urvival was inhibited by co-incubation with either H 7 (10 mu mol/l) o r H 8 (20 mu mol/l), which worked as protein kinase C inhibitors. Alth ough our study did not measure neutrophil survival in vivo directly, i t provides us with further evidence that rhG-CSF may function to prolo ng neutrophil life expectancy in vivo.