When similar numbers of PBMCs from RA patients and healthy controls were cultured in osteoclastogenic conditions (cultured under the presence of the receptor activator of nuclear factor-κB ligand (RANKL) with macrophage colony-stimulating factor (M-CSF)), more osteoclasts formed in the RA than the control culture. The gene discussed is TNFSF11; the disease is rheumatoid arthritis.