It has been found that an increased proportion of M2 macrophages in RA synovial tissues is associated with lower RA disease activity and synovial inflammation, with anti-inflammatory and homeostatic functions (44), whereas synovial macrophages in healthy synovial tissues are predominantly CD206-positive macrophages, the M2 macrophages, which play an important role in the maintenance of tissue homeostasis (45). This evidence concerns the gene MRC1 and rheumatoid arthritis.