A further aspect that could be strictly related to the M1/M2 macrophages role and their involvement in the development of different systemic degenerative diseases not only seen in bone decay but in pulmonary fibrosis (PF), neural-degenerative disease such as Alzheimer’s (AD) as well, is the chemoattractant role of MIF as ligand for CXCR4, in the recruitment of circulating osteoclast precursors (OCPs) to the bone lytic lesion. The gene discussed is CXCR4; the disease is pulmonary fibrosis.