Recently, Hidetoshi Sugihara reported that PGRN deficiency led to an increase of M2 macrophages in regenerating muscle, and prolonged the persistence of macrophages (possibly M2 type), suggesting that M1 and M2 macrophage populations may vary under different health conditions and the outcome of bacterial infection is contingent on dominant macrophage microenvironments (45). The gene discussed is GRN; the disease is bacterial infectious disease.