FPR2 and rheumatoid arthritis: Here, we showed that a novel FPR2 agonist (scolopendrasin IX) elicited strong therapeutic effects against the K/BxN serum-transfer arthritis model (Fig. 4), which was blocked by an FPR2 antagonist (WRW4) (Fig. 6), suggesting that stimulation of FPR2 resulted in therapeutic activity against RA.