ACPAs Are Much More Than Diagnostic Autoantibodies

Anti-citrullinated protein autoantibodies (ACPAs) are the major autoantibodies in rheumatoid arthritis (RA). Anti-citrullinated protein autoantibodies are directed against different citrullinated antigens, including filaggrin, fibrinogen, vimentin, and collagen. Presence of ACPA is associated with joint damage and extra-articular manifestations, suggesting that ACPAs are most likely pathogenic autoantibodies in RA. In vitro, ACPAs induce macrophage tumor necrosis factor alpha (TNF-α) production, osteoclastogenesis, and complement activation. These autoantibodies also induce the formation of neutrophil extracellular traps (NETs). Additionally, ACPAs induce pathogenic cytokines expression and oxidative stress in immune cells derived from RA patients. The aim of this review is to show the pathogenic roles of these autoantibodies in RA.