Increased serum flt3-ligand in healthy donors undergoing granulocyte colony-stimulating factor-induced peripheral stem cell mobilization

The effect of granulocyte colony-stimulating factor (G-CSF) induced mobilization of peripheral blood progenitor cells (PBPC) on the endogenous serum levels of cytokines stem cell factor (SCF) and flt3-ligand (flt3-L) was studied in 18 healthy subjects undergoing allogeneic PBPC donation. Donors received a standardized mobilization regime consisting of a 4-day course of G-CSF, with leukapheresis on day 5. Endogenous serum flt3-L and SCF were determined prior to G-CSF administration, on the day of leukapheresis, and followed up until day +100 after cessation of G-CSF administration. The administration of G-CSF resulted in a transient elevation of endogenous flt3-L serum levels. At the day of leukapheresis serum flt3-L showed a median increase of 75% compared to serum flt3-L levels obtained before G-CSF treatment. The increase in serum flt3-L levels showed no correlation with the total number of progenitor cells mobilized. Cessation of G-CSF treatment led to normalization of serum flt3-L within 7 days post G-CSF administration. In contrast, serum CSF levels remained unchanged in response to G-CSF administration. Our results demonstrate a transient surge in serum flt3-L in relation to G-CSF-induced PBPC mobilization, although the assessment of endogenous flt3-L give no information regarding the ability for G-CSF-induced PBPC recruitment in healthy individuals.