CFUGEMM, CFUGM, CFUMK: analysis by equilibrium density centrifugation.

A modification of the technique of Fauser and Messner was used for the culture of human multipotent hematopoietic progenitors. This modified technique shows a linear relationship between mixed granulocytic-erythrocytic colonies and the number of cells plated, even at extremely low cell doses (10(4) cells/dish) and is therefore a more suitable assay system for cell separation studies than the original non-linear method. The buoyant density of CFUGEMM (colony forming unit granulocytic-erythrocytic-megakaryocytic-macrophage) was determined using equilibrium density centrifugation. CFUGEMM were of lower buoyant density than the majority of nucleated marrow cells. Substantially enriched populations of CFUGEMM could be obtained with a single density separation procedure. The density distribution profile for CFUGEMM was also distinct from the density distribution of granulocyte-macrophage colony forming cells (CFUGM), the latter being of somewhat greater buoyant density than the former. Cells which formed clones containing only megakaryocytes in culture (CFUMK) had an intermediate density between that of CFUGEMM and CFUGM. The morphological characteristics of these progenitor cells were studied using correlation analysis. Results suggested that the CFUGEMM correspond to transitional cells without granules, the CFUGM to transitional cells with 1-4 granules and the heterogeneous group of GM-cluster forming cells to a broad category including myeloblasts, promyelocytes, myelocytes and metamyelocytes.