Purification of human granulocyte-macrophage progenitor cells (CFU-C) using indirect immunofluorescence and cell sorting.

We have attempted to purify human bone marrow granulocyte-macrophage progenitor cells utilizing purified stimulating factor, indirect immunofluorescence and cell sorting. These cells can be labelled by sequential incubation with colony-stimulating factor (CSF), rabbit anti-CSF antibody and fluorescently labelled goat anti-rabbit gamma globulin. Flow photometry demonstrated that binding of CSF to marrow cells varied with CSF concentration and duration of incubation. Marrow cells were pre-concentrated by incubation with carbonyl iron followed by Percoll gradient centrifugation and then labelled by this indirect immunofluorescence method. Sorting of these cells yielded up to 95-fold purification of colony-forming cells and fractions containing in excess of 10% colony- and cluster-forming cells.