Marker analysis of cloned populations of human monocytes

The presence of myelomonocytic progenitor cells in human peripheral blood was used for the analysis of cloned populations of human monocytes. Colonies of granulocytes and macrophages were obtained by plating peripheral blood mononuclear cells (PBM) in methylcellulose containing medium in the presence of medium conditioned by nonstimulated PBM (CM). Following 20-25 days of incubation, most colonies were found to consist of cells with monocyte-macrophage morphology. Cloned populations of monocytes were tested for several monocyte membrane markers and compared to noncloned adherent monocytes. HLA-DR, 63D3, LeuM2 antigens and Fc receptors were expressed on cells from individual colonies in similar proportions to their expression on noncloned monocytes. Some colonies were uniform in their negative expression of the 63D3 antigen, as were the noncloned monocytes. Although the clonality of cells tested was not directly proven, these results indicated that at least for some monocyte markers, heterogeneous expression was obtained in monoclonal populations of monocytes. It is possible, however, that testing of additional markers and functions may reveal homogeneous clones of monocytes and suggest the existence of stable subsets.