The kinetic participation of macrophages, especially M1 to M2 transition, is critical in the healing of myocardial infarction (MI).However, the mechanisms underlying M1/M2 polarization during this process have not been fully understood.Prostaglandin D2 (PGD2) has been proposed to protect heart against ischemia/reperfusion injury.Here, we found that the deletion of PGD2 receptor DP1 in macrophages (Mac-DP1 KO) retarded M2 macrophage polarization and reduced the production of anti-inflammatory cytokines both in vitro and in a couple of inflammatory models in vivo.