An Improved Negative Immunomagnetic Selection Strategy for the Purification of Primitive Hemopoietic Cells from Normal Bone Marrow

An improved negative immunomagnetic selection strategy has been devised for the enrichment of primitive hemopoietic cells using the high proliferative potential colony-forming cell (HPP-CFC) assay as an index of stem cell purification. Immunomagnetic selection was carried out using goat anti-rat conjugated M-450 Dynabeads and a cocktail of rat monoclonal antibodies directed against lineage antigens expressed on B-lymphocytes (B220), neutrophils and activated macrophages (7/4), differentiating erythroid cells (YW 25.12.7), and T-lymphocyte subsets (Lyt-2 and L3T4). This negative selection strategy results in the highly reproducible enrichment of HPP-CFC with negligible loss of HPP-CFC at the immunomagnetic selection step. A 30-fold enrichment of HPP-CFC stimulated by interleukin 3 (IL-3) plus colony-stimulating factor (CSF-1), or interleukin 1 alpha (IL-1 alpha) plus IL-3 plus CSF-1, is obtained with simultaneous resolution of HPP-CFC from progenitor cells of low proliferative potential responsive to CSF-1 alone (LPP-CFC). Flow cytometric analysis of these lineage-negative cells reveals that they almost exclusively exhibit the light-scattering characteristics of blast cells and the morphology of a candidate hemopoietic stem cell. Positive fluorescence-activated cell sorting of immunomagnetically pre-enriched normal bone marrow cells using wheat germ agglutinin yields cell preparations with a cloning efficiency of up to 45% and a HPP-CFC content of 20%.