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Pluripotent hemopoietic progenitors in human bone marrow can be identified by their ability to give rise in culture to colonies that contain more than one lineage of hemopoietic differentiation. Growth of these mixed colonies is supported by media conditioned by leukocytes in the presence of phytohemagglutinin (PHA-LCM) and erythropoietin. They can be readily recognized by direct microscopic observation because of their composition of colorless cells and cells with a red appearance typical for hemoglobin. Seventy-three individual mixed colonies from 6 individuals were prepared by cytocentrifugation for further cytological examination. In addition to neutrophilic granulocytes and erythroblasts, megakaryocytes were present in 16 of the 73 colonies, as identified by positive reaction for acid phosphatase. Macrophages were found in 24 and eosinophils in 6 of the 73 colonies.
Fauser et al. (Tue,) studied this question.