A flow cytometric method to quantify the Granulocyte-macrophage colony-stimulating factor receptor (GM-CSFr) on human cells is described. The number of GM-CSFr binding sites on human neutmphils was assessed by using Merent bead standards. Results were compared with those from conventional receptor quantification, which was petformed by using the radioligand binding assay. A high degree of correlationwas found between the two methods, although quantitative evaluation of GM-CSFr expression on neutmphils performed by flow cytometry revealed a somewhat higher number of receptor molecules per cell than with that determined by Scatchard analysis. By the flow quantitative approach, we measured the GM-CSFr on mobilized CD34-positive cells and obtained results similar to those of previously published data.
Our data suggest that flow cytometric analysis is a simple and reproducible method to detect and quantify the presence of GM-CSFr per cell, thus allowing the study of receptor expression on different populations selected by gating on the basis of the scatter parameters and sutface markers. This assay offers the possibility to quantify the presence of GM-CSFr on Merent subsets of normal and pathological cells even if samples are too small (such as CD3Cpositive progenitor cells) for measurement with the radioligand binding assay.