Exclusive expression of G-CSF receptor on myeloid progenitors in bone marrow CD34[sup +] cells.

Summary. Although granulocyte colony-stimulating factor (G-CSF) has been reported to act on cells of neutrophilic lineage, the administration of G-CSF to induce the mobilization of various haematopoietic progenitors into the circulation. We analysed the expression of receptors for G-CSF (G-CSFR) on human bone marrow and G-CSF-mobilized peripheral blood CD34[sup +] cells, and examined the proliferation and differentiation capabilities of sorted CD34[sup +] G-CSFR[sup +] and CD34[sup +] G-CSFR[sup -] cells using methylcellulose clonal culture. Flow cytometric analysis showed that G-CSFR was expressed on 14·9 ± 64·9% of bone marrow CD34[sup +] cells, most of which were included in CD34[sup +] CD33[sup +] and CD34[sup +] CD38[sup +] cell fractions. In clonal cultures, CD34[sup +] G-CSFR[sup +] cells produced only myeloid colonies, whereas CD34[sup +] G-CSFR[sup -] cells produced erythroid bursts, megakaryocyte and multilineage colonies. When incubated with the cytokine cocktail for 5 d, CD34[sup +] G-CSFR[sup -] cells generated CD34[sup +] G-CSFR[sup +] myeloid progenitors. In G-CSF-mobilized peripheral blood, CD34[sup +] cells contained 10·8 ± 5·8% of G-CSFR[sup +] cells, most of which were also myeloid progenitors, although CD34[sup +] G-CSFR[sup -] cells contained a substantial number of myeloid progenitors. These results indicated that the expression of G-CSFR on CD34[sup +] cells is restricted to myeloid progenitors, suggesting that the specific activity of G-CSF on myelopoiesis depends on the exclusive expression of its receptor on myeloid progenitors, and that the mobilization of various haematopoietic progenitors is not a direct effect of G-CSF in humans. [ABSTRACT FROM AUTHOR]