Enrichment of progenitor cells from human marrow.

Suspensions enriched for myeloid and erythroid colony-forming cells were prepared from human marrow by simultaneous treatment of low-density cells with the monoclonal antibodies Campath-1 and 80H.3, followed by immune-rosetting; lymphocytes and monocytes were successfully removed by this method. The final suspension contained 22% of blasts and 70% primitive myeloid-monocytic cells. GM-CFCs, counted after 14 days of culture, were enriched 21-fold. Of all cells present in the final suspension, 10.8% were day 8 GM cluster-forming cells, 2.3% were day 8 GM colony-forming cells, 2.4% were day 7 CFU-E, 0.9% were day 14 GM cluster-forming cells, 1.1% were day 14 GM colony-forming cells, and 0.6% were day 14 BFU-E. After enrichment, BFU-E became markedly more dependent on the addition of 5637-conditioned medium as a source of growth factors, suggesting that lymphocytes and/or monocytes support erythroid progenitor growth in cultures of unfractionated marrow. By removing these cells, we obtained a sensitive assay for burst-promoting activities in conditioned media. This procedure can be used to study the roles of marrow lymphocytes and monocytes in hemopoiesis as well as providing a basis for the purification of normal and aberrant progenitors.