2022 Volume 34 Issue 1 Pages 51-59
Rheumatoid arthritis（RA）can be defined as a “systemic autoimmune disease characterized by anti-citrullinated protein antibody（ACPA）”. ACPA or rheumatoid factor（RF）may be found in serum more than 10 years before the onset of RA and their positive rate is increasing as the onset of RA approaches, with epitope spreading for ACPA. It is also known that the titers of ACPA and RF are sharply elevated just before the onset of RA. If ACPA is positive, cortical bone damage begins even without RA synovitis, but little abnormalities are observed in the trabecular number and/or thickness. Therefore, activation of inflammatory cytokines is necessary to complete the RA pathology. It is reported that ACPA immune complex is recognized by macrophages via FcγR and enhances the secretion of TNF-α and IL-6. The importance of RF in this setting has been determined. Since ACPA-positive individuals are considered to be in the “pre-RA” state, clinical trials have been reported in which rituximab and abatacept are administered to such individuals to prevent the onset of RA. Thus, autoantibodies may have clinical significance for considering RA “at risk” condition.
