Different membrane expression of CD11b and CD14 on blood neutrophils following in vivo administration of myeloid growth factors

During the administration of recombinant human granulocyte colony-stimulating factor (rhG-CSF) or granulocyte-macrophage CSF (rhGM-CSF) we studied the early and late changes of membrane antigen density on neutrophils. RhG-CSF and rhGM-CSF both caused an early transient reduction in blood neutrophilic granulocyte-concentration within the first 30 min after treatment followed by a marked later increase during the subsequent 24 h. During the early neutropenia quantitative flow cytometry showed an associated marked increase in the density of membrane CD11b from 169 x 10(3) before to 568 x 10(3) A.U. per cell induced by rhGM-CSF but a non-significant change by rhG-CSF, suggesting that different mechanisms may be responsible for the transient neutropenia. The subsequent neutrophil granulocytosis was followed by a significantly (P < 0.05) increased density of the CD14 antigen from 6.1 x 10(3) before to 15.9 x 10(3) A.U. per cell during treatment with rhG-CSF, but not by rhGM-CSF administration. These results demonstrate that the two cytokines may affect the function of neutrophilic granulocytes in different ways. The increased expression of CD11b could explain some of the side-effects during treatment with rhGM-CSF. The upregulation of CD14 induced by rhG-CSF may be clinically relevant, as CD14 is an opsonic receptor for lipopolysaccharide binding proteins, acting in the defence against Gram-negative bacterial infections.