Isolation and analysis of primitive hemopoietic progenitor cells on the basis of differential expression of Qa-m7 antigen

In the presence of the hemopoietic growth factor CSF-1, the later committed cells of the macrophage lineage can be detected by their ability to form small colonies in clonal agar culture (CFC(CSF-1)). Synergistic factors have been described that in combination with CSF-1 stimulate developmentally early hemopoietic progenitor cells of high proliferative potential (HPP-CFC). By using a monoclonal antibody to the Qa-m7 antigenic determinant, we investigated and compared the expression of Qa-m7 on CFC(CSF-1) and on HPP-CFC of two types that grow in response to either 1) CSF-1 plus synergistic factor from human placenta-conditioned medium (HPP-CFC(Hplac+CSF-1)) or 2) CSF-1 plus synergistic factor from conditioned medium of the WEHI-3 myelomonocytic cell line (HPP-CFC(W+CSF-1)). We have shown that HPP-CFC of both types express relatively more Qa-m7 antigen then CFC(CSF-1) and can be separated and enriched on this basis by discontinuous buoyant density centrifugation and fluorescence-activated cell sorting of normal bone marrow. Significant enrichments of HPP-CFC(HPlac+CSF-1) (43.5-fold) and HPP-CFC(W+CSF-1) (28.8-fold) have been achieved with cloning efficiencies of HPP-CFC in the most enriched fractions reaching 4 to 5%. These results clearly illustrate the fact that there are populations of progenitor cells from normal, unperturbed bone marrow that strictly require a combination of two hemopoietic growth factors (CSF-1 plus synergistic factor) in order to be detected.