Characterization of a human hematopoietic progenitor cell capable of forming blast cell containing colonies in vitro.

A hematopoietic cell (CFU-B1) capable of producing blast cell containing colonies in vitro was detected using a semisolid cul- ture system. The CFU-B1 has the capacity for self-renewal and commitment to a number of hematopoietic lineages. Monoclonal antibody to the human progenitor cell antigen-i (HPCA-1) and a monoclonal antibody against the major histo- compatibility class II antigen (HLA-DR) were used with fluo- rescence activated cell sorting to phenotype the CFU-B1. The CFU-B1 was found to express MylO but not HLA-DR antigen; experiments using complement-dependent cytotoxicity to elim- inate DR positive cells confirmed this finding. Pretreatment of marrow cells with two chemotherapeutic agents, 5-fluorouracil and 4-hydroperoxycyclophosphamide facilitated detection of CFU-B1 derived colonies, while diminishing or totally inhibit- ing colony formation by other hematopoietic progenitor cells. CFU-Bl-derived colony formation was dependent upon the addition of exogenous hematopoietic growth factors. Media conditioned either by the human bladder carcinoma cell line 5637 or lectin stimulated leukocytes, as well as recombinant granulocyte-macrophage colony stimulating factor, interleukin 3 or interleukin la promoted blast cell colony formation. By contrast, neither recombinant erythropoietin, recombinant in- terleukin 4, purified macrophage colony stimulating factor or recombinant granulocyte colony-stimulating factor alone pro- moted blast cell colony formation.