On the one hand, osteoclasts differentiate and activate in the presence of macrophage colony-stimulating factor (M-CSF) and RANKL, which increase during periodontitis mainly by Th17 activity; while on the other hand, osteoblasts produce osteoprotegerin (OPG), the RANKL soluble decoy, which is partly mediated by Treg lymphocyte activity during periodontitis (17, 23, 27–31). Here, CSF1 is linked to periodontitis.