Developmental and Comparative Immunology

abstract Macrophage colony-stimulating factor (CSF1) controls the proliferation and differentiation of cells of the 25 mononuclear phagocyte system. CSF1, alongside a second ligand, interleukin-34 (IL-34), acts by binding 26 to a cell surface receptor (CSF1R). We previously cloned and expressed pig CSF1 and IL-34. Here we pro- 27 duced a pig CSF1R-Ig + pFUSE Fc fusion protein and used it as an immunogen to produce three monoclo- 28 nal antibodies (ROS8G11, ROS3A5 and ROS3B10) targeted against porcine CSF1R. Specific binding of each 29 monoclonal antibody was confirmed by ELISA, Western blot, flow cytometry and immunocytochemistry. 30 The antibodies did not block CSF1 signalling. The surface expression of CSF1R in pig peripheral blood was 31 restricted to CD14-positive monocytes and was also detected on lung macrophages. These antibodies 32 provided an opportunity to investigate the increase of available CSF1R during pig BMDM differentiation. 33 The new monoclonal antibodies provide useful reagents to support the study of monocyte and