Human recombinant macrophage colony stimulating factor activates murine Kupffer cells to a cytotoxic state

Activated macrophages mediate cytotoxicity against tumor targets and thus may modulate development and growth of metastatic tumor cells. Macrophage colony stimulating factor (M-CSF) has a potential role in activating mature macrophages to a cytotoxic state. We employed a muring Kupffer cell (KC) model of cytotoxicity against a tumor necrosis factor (TNF) - sensitive murine colon adenocarcinoma cell line (MCA26) to evaluate the ability of recombinant human M-CSF (rhM-CSF) 1) to act alone as a KC-activating agent and 2) to enhance KC cytotoxicity against MCA26 cells in association with known macrophage activating compounds. rhM-CSF produced a dose-dependent increase in TNF release by KC in vitro with a parallel increase in MCA26 killing. KC activated by rhM-CSF produced less TNF and concomitantly demonstrated a lower cytotoxicity against MCA26 cells when compared with KC activated by gamma interferon (γIFN) with or without lipopolysaccharide (LPS). M-CSF did not act in a synergistic fashion with γIFN and LPS to increase TNF secretion or cytotoxicity against MCA26 cells. rhM-CSF thus acts as a single agent capable of activating murine KC to a cytotoxic state but does not cooperate with classical priming/triggering signals to achieve KC activation.