Development and characterisation of monoclonal antibodies reactive with porcine CSF1R (CD115)

• We have produced the first monoclonal antibodies against the CSF1 receptor in pigs.
• As in other mammals, surface CSF1R is a monocyte macrophage marker and is induced during macrophage differentiation.
• The antibodies do not block CSF1 signalling.
• In bone marrow progenitors, a large proportion of the receptor is within the cell and revealed upon starving the cells of CSF1.

Macrophage colony-stimulating factor (CSF1) controls the proliferation and differentiation of cells of the mononuclear phagocyte system. CSF1, alongside a second ligand, interleukin-34 (IL-34), acts by binding to a cell surface receptor (CSF1R). We previously cloned and expressed pig CSF1 and IL-34. Here we produced a pig CSF1R-Ig + pFUSE Fc fusion protein and used it as an immunogen to produce three monoclonal antibodies (ROS8G11, ROS3A5 and ROS3B10) targeted against porcine CSF1R. Specific binding of each monoclonal antibody was confirmed by ELISA, Western blot, flow cytometry and immunocytochemistry. The antibodies did not block CSF1 signalling. The surface expression of CSF1R in pig peripheral blood was restricted to CD14-positive monocytes and was also detected on lung macrophages. These antibodies provided an opportunity to investigate the increase of available CSF1R during pig BMDM differentiation. The new monoclonal antibodies provide useful reagents to support the study of monocyte and macrophage biology in the pig.