FPR2 and rheumatoid arthritis: Previously, the function of FPRs was investigated in autoimmune arthritis,22, 23 and it was known that serum amyloid A, an another endogenous FPR2 agonist, mediates synovial hyperplasia and angiogenesis via FPR2 of synovial fibroblasts during progress of RA.24, 25