RF and anti-citrullinated protein antibodies (ACPA) in RA patients can form immune complexes with citrullinated proteins in the synovium and subsequently activate synovial macrophages, resulting in the production of proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6, which are the central processes in the pathogenesis of RA [33]. Here, PRTN3 is linked to rheumatoid arthritis.