Characterization of hemopoietic activities in media conditioned by a murine marrow-derived adherent cell line, B.Ad

The hemopoietic activities present in medium conditioned by a murine bone marrow-derived adherent cell line (B.Ad) have been studied. B.Ad-conditioned medium stimulated neutrophil, neutrophil-macrophage, and macrophage colonies in agar cultures of bone marrow cells and 90% of this activity was neutralized by antimacrophage colony-stimulating factor (anti-M-CSF). The conditioned medium supported the generation and/or maintenance of spleen colony-forming units (CFU-S) in liquid cultures and synergized with multilineage colony-stimulating factor (Multi-CSF; IL-3) to stimulate colony formation by day-3 post-5-fluorouracil (FU)-treated bone marrow cells. When used as feeder layers, B.Ad cells stimulated erythroid colony-forming units (CFU-E) and markedly enhanced erythroid burst-forming units (BFU-E) stimulation more than did maximal Multi-CSF (IL-3) and Epo stimulation. No CFU-E- or BFU-E-stimulating activities were detected in medium conditioned by B.Ad cells. Similarly, B.Ad-conditioned medium was unable to stimulate Multi-CSF (IL-3) or granulocyte-macrophage (GM)-CSF-dependent cell lines. The data suggest that medium conditioned by this bone marrow-derived adherent cell line contains M-CSF and other factors not detectable as CSFs that either directly or by means of a synergistic mechanism are able to stimulate CFU-S and colony-forming cells (CFC).