Megakaryocytic cells in mixed haemopoietic colonies (CFU-GEMM) from the peripheral blood of normal individuals

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Abstract
The cellular composition of mixed hemopoietic colonies CFU-GEMM [pluripotent progenitor cells] from the peripheral blood of normal individuals was investigated using both an improved in vitro culture assay and a monoclonal antibody reactive with the earliest megakaryocytic precursor cells. The frequency of CFU-GEMM was found to be 22 .+-. 7/ml blood (mean .+-. SE; n = 8) and 4.9 .+-. 1.8/106 mononuclear cells. Double-labeling of single colonies with monoclonal antibodies against megakaryocytic as well as granulocytic cells revealed that only 18% of mixed colonies from the peripheral blood contained megakaryocytic cells as compared to 87% of mixed colonies from the bone marrow, while no difference existed with regard to granulocytic cells. Circulating multilineage progenitor cells either require different culture conditions to express their megakaryocytic component or, alternatively, that the circulating pluripotent stem cell pool mainly consists of bipotent rather than multipotent progenitor cells.