MACROPHAGES KILL T9 GLIOMA TUMOR-CELLS BEARING THE MEMBRANE ISOFORM OF MACROPHAGE-COLONY-STIMULATING FACTOR THROUGH A PHAGOCYTOSIS-DEPENDENT PATHWAY

Rat T9 glioma cells transfected with the gene for the membrane isoform of macrophage-CSF (mM-CSF) but not for the secreted isoform of M-CSF were directly killed by bone marrow-derived macrophages. Macrophage-me diated cytolysis of the mM-CSF-transfected clone was blocked by using chemical inhibitors of phagocytosis such as iodoacetate, 2-deoxyglucos e, gadolinium chloride, and cytochalasin B, In contrast, macrophage-me diated killing of mM-CSF-expressing tumor cells was augmented by the m icrotubule inhibitor, colchicine, Use of nitric oxide and reactive oxy gen intermediate inhibitors failed to alter the macrophage-mediated ki lling of the mM-CSF-transfected tumor cells, Photomicroscopy, using im munohistochemical staining with the anti-Hck Ab to distinguish macroph ages from tumor cells, revealed that phagocytosis began within 2 h aft er addition of the mM-CSF-bearing tumor cells. Photocinematography con firmed that macrophages first phagocytosized and then lysed the intern alized mM-CSF transfectant cells. Using annexin V and acridine orange staining techniques, macrophages phagocytosized living mM-CSF-transfec ted tumor cells.