In vitro activation of rGM‐CSF derived bone marrow macrophages by cisplatin and lipopolysaccharide

Treatment of fresh non-adherent bone marrow cells (NABMC) with cisplatin or lipopolysaccharide (LPS) did not render them tumoricidal. NABMC incubated in medium alone or medium containing recombinant granulocyte macrophage colony stimulating factor (rGM-CSF) for 4 days matured to macrophages that were positive for non-specific esterase staining. Bone marrow-derived macrophages cultured with medium alone did not respond to cisplatin or LPS by the induction of tumoricidal activity, whereas rGM-CSF derived bone macrophages showed significantly enhanced cytotoxicity after treatment with cisplatin or LPS. Culturing of NABMC with rGM-CSF enhanced cell survival compared to the cells incubated in medium alone. These results suggest that bone marrow cells not only mature in rGM-CSF, but are also primed by rGM-CSF for induction of tumoricidal activity.