Granulocyte colony-stimulating factor (G-CSF) transiently suppresses mitogen-stimulated T-cell proliferative response

Granulocyte colony-stimulation factor (G-CSF) is a cytokine that selectively promotes growth and maturation of neutrophils and may modulate the cytokine response to inflammatory stimuli. The purpose of this study was to examine the effect of G-CSF on ex vivo peripheral blood mononuclear cell (PBMC) functions. Ten patients with breast cancer were included in a clinical trial in which r-metHuG-CSF was administered daily for 5 days to mobilize peripheral blood stem cells. Ten healthy women were also included as controls. Our data show that G-CSF treatment induces an increase in peripheral blood leucocyte, neutrophil, lymphocyte and monocyte counts. We have found a modulation in the percentages of CD19+, CD45+ CD14+, CD4+ CD45RA+ and CD4+ CD45RO+ cells in PBMC fractions during G-CSF treatment. We have also found a significant reduction in the proliferative response of PBMC to mitogenic stimulation that reverted 14 days after the fifth and the last dose of G-CSF. Furthermore, it was not associated with significant changes in the pattern of cytokine production. The mechanism of this immunoregulatory effect is probably indirect since G-CSF receptor has not been found in T lymphocytes. This mechanism and its potential clinical applications remain to be elucidated.