Expression of granulocyte colony-stimulating factor receptor increases with differentiation in myeloid cells by a newly-devised quantitative flow-cytometric assay.

In order to develop a non-isotopic quantitative assay of granulocyte colony-stimulating factor (G-CSF) receptors on human or murine cells, we devised a flow-cytometric assay using cells stained with biotin-labelled G-CSF (b-G-CSF) and a streptavidin-RED670 conjugate. For quantification, we applied the Kolmogorov-Smirnov test and calculated the D value. The D value was evaluated from the degree of shift in two fluorescence profiles according to the increase of fluorescence intensity due to the specific binding of b-G-CSF to G-CSF receptors. A good correlation was observed between the number of G-CSF receptors obtained by the radioisotopic binding assay and the number calculated from the D value by the flow-cytometric assay. Then, expression of G-CSF receptors on human bone marrow cells, peripheral blood granulocytes and blast cells from patients with acute myeloid leukaemia (AML) were studied. G-CSF receptors was expressed on CD34+CD33-, CD34+CD33+ and CD34-CD33+ cells in the following order: CD34-CD33+ > CD34+CD33+ > CD34+CD33- cells, indicating that the receptors increased with maturation. The receptor levels of CD34-CD33+ cells in bone marrow were apparently lower than those of CD34-CD33+ cells in peripheral blood granulocytes. On the other hand, an abnormal expression pattern of G-CSF receptors was noted in AML blast cells.