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

A progenitor cell CFU-B1 (blast cell colony forming unit) present in human bone marrow and capable of producing blast cell containing colonies in vitro was detected using a serum containing semisolid culture system. The CFU-B1 has the capacity not only to undergo self-renewal, but also commitment to a number of hematopoietic lineages. This progenitor cell therefore has characteristics which suggest that it is identical to or closely related to the human pluripotent hematopoietic stem cell. Pretreatment of marrow cells with 5 fluorouracil facilitated detection of CFU-B1 derived colonies. The formation of CFU-B1 derived colonies was dependent upon the addition of media conditioned by the human bladder carcinoma cell line 5637. The ability of 5637 CM (conditioned media) to support blast cell colony formation was in part but not totally ablated by pretreatment of the CM with an IL-1 alpha (interleukin-1) neutralizing antibody. This data suggests that IL-1 alpha plays a role in the regulation of primitive events occurring during human hematopoiesis. IL-1 alpha might be exerting these effects by either acting directly on the CFU-B1, causing marrow accessory cells to elaborate other cytokines or by synergizing with cytokines already present in 5637 CM.