Monoclonal antibodies that specifically inhibit GM-CSF- and IL-3-dependent growth of human monocytic leukemia cells

We describe monoclonal antibodies (mAbs: anti-MaG-1, TGI-1, TGI-5, and TGI-6) that block the proliferation of AML-193 cells in response to GM-CSF or IL-3 and do not affect the proliferation of AML-193 cells in response to G-CSF and IL-2-driven proliferation of Kit 225 cells. However, none of the mAbs tested had any stimulative effect on the proliferation of AML-193 cells. The mAbs (anti-MaG-1, TGI-1, -5, and -6) could inhibit the binding of [125I]GM-CSF to AML-193 cells. We were able to purify MaG-1 Ag by anti-MaG-1 affinity chromatography. Thus, the MaG-1 Ag and the Ags recognised by mAbs (TGI-1, -5, and -6) may be associated with the receptor for GM-CSF or IL-3 or a structure close to the receptor for GM-CSF or IL-3.