Stromal growth factor production in irradiated lectin exposed long-term XXXX bone marrow cultures.

@entity19 @entity2304 @entity9827 @entity3019
Hematopoietic regulatory factors produced by adherent (stromal) cells in long-term @entity19 bone marrow cultures have been investigated. Using an in situ double layer agar overlay system, we demonstrated that exposure of the stromal cells to 1,100-rad irradiation increased their activities in stimulating colony formation of FDC-P1, an @entity3019 ( @entity3019 )-responsive cell line. The colony-stimulating activities (CSAs) of the irradiated stroma also stimulated normal marrow cells to form granulocyte-macrophage, megakaryocyte, and mixed lineage colonies. Addition of the lectin pokeweed mitogen to the irradiated stroma increased the level of CSAs. The FDC-P1 CSA of the irradiated stroma was inhibited by antibodies directed against @entity19 @entity2304 ( @entity2304 ) but not by those against @entity19 @entity3019 . Stromal-derived CSA for marrow cells was also partially blocked by anti- @entity2304 antibodies, probably reflecting the presence of other CSAs such as @entity9827 . This latter growth factor has been found to be present in conditioned media from Dexter stroma, but levels are not increased after irradiation or lectin exposure. Partially purified @entity2304 , like @entity3019 , stimulated FDC-P1 proliferation and granulocyte, macrophage, and megakaryocyte colony formation. These results indicate that the major terminal differentiating hormone elicited by irradiation or lectin exposure of @entity19 marrow stromal cells is @entity2304 . This growth factor, along with @entity9827 , can account for the differentiated progeny produced in this system: macrophages, granulocytes, and megakaryocytes.
