Inhibition of colony-stimulating factor-1 activity by monoclonal antibodies to the human CSF-1 receptor

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• The colony-stimulating factor-1 receptor (CSF-1R), also known as c-fms, plays a crucial role in the proliferation and survival of mononuclear phagocytes.
• Understanding CSF-1R signaling is vital for therapeutic interventions targeting myeloid cell development and function.

Purpose of the Study:

• To develop and characterize monoclonal antibodies (MoAbs) that specifically inhibit CSF-1R function.
• To investigate the effects of these MoAbs on CSF-1 binding, cellular proliferation, and receptor signaling.

Main Methods:

• Generation of 12 monoclonal antibodies against the extracellular domain of human CSF-1R.
• Assays to measure CSF-1 binding inhibition, colony formation, and ligand-independent proliferation.
• Analysis of CSF-1R internalization and degradation upon antibody treatment.

Main Results:

• Four out of 12 MoAbs specifically inhibited CSF-1 binding to CSF-1R-bearing cells.
• These four MoAbs abrogated CSF-1-dependent colony formation in human macrophage precursors and engineered NIH-3T3 cells.
• One MoAb (2-4A5) interfered with ligand-independent proliferation in oncogenically transformed NIH-3T3 cells.
• Inhibitory MoAbs did not induce CSF-1R internalization or degradation, unlike CSF-1 itself.

Conclusions:

• Monoclonal antibodies targeting specific epitopes on CSF-1R can effectively block CSF-1 binding and inhibit downstream signaling.
• These novel MoAbs are valuable tools for identifying and quantifying CSF-1R and for abrogating CSF-1R-mediated signals.
• The developed antibodies hold potential for therapeutic applications in conditions involving mononuclear phagocyte dysregulation.