Nevertheless, thorough investigation is needed to delineate the exact effect of CCP on the RANKL/RANK/OPG axis in RA, and to clarify whether CCP could regulate the expression of OPG on osteoblast or it could affect the cytokines milieu within the inflamed sites of bone erosion in arthritis. The gene discussed is TNFRSF11A; the disease is arthritic joint disease.