Bone marrow adjacent to the RA joints contains an increased number of granulocyte-macrophage progenitors, colony-forming unit granulocyte-macrophages (CFU-GM), which can differentiate into granulocytes or macrophages with GM-CSF stimulation [83] and also into osteoclasts with M-CSF and RANKL stimulation [84]. Here, CSF2 is linked to rheumatoid arthritis.