OBJECTIVETo investigate the effect of granulocyte colony stimulating factor (G-CSF) on myeloid-derived suppressor cells (MDSCs) in the bone marrow and peripheral blood, and explore the relationship between MDSC and graft-versus-host disease (GVHD).

METHODSBone marrow, peripheral blood and peripheral blood stem cells were obtained from 12 healthy hemopoietic stem cell donors before and on day 5 after G-CSF mobilization. Flow cytometry was employed to examine the number of MDSC, and the relationship between MDSC number and the incidence of GVHD was analyzed.

RESULTSIn normal physiological conditions, MDSC could be detected in the peripheral blood and bone marrow with a cell percentages of (1.35±0.35)% and (2.44±1.11)%, respectively, showing a significantly higher cell percentage in the bone marrow (P=0.015). On the 5th day after G-CSF mobilization, the percentage of MDSCs increased to (4.01±1.82)% in the peripheral blood and to (4.38±2.19)% in the bone marrow, showing no significant difference between them (P=0.083). The mobilization caused a significant increase in the number of MDSCs in the peripheral blood (P=0.047) but not in the bone marrow (P=0.761). The number of MDSCs in the collected samples showed a significant inverse correlation to the incidence of GVHD (P=0.048).

CONCLUSIONSMDSCs are present in the peripheral blood and bone marrow of healthy donors, with a greater number in the bone marrow. G-CSF can mobilize the MDSCs from the bone marrow to the peripheral blood to increase number of MDSCs in the peripheral blood, which may contribute to a lowered incidence of GVHD in hematopoietic stem cell transplantation (HSCT).