The characteristics of regulatory macrophages and their roles in transplantation

•Regulatory macrophage (Mreg) have immunosuppressive and anti-inflammatory properties.•Mreg could delete activated T cells, induce Tregs and secrete effector molecules.•Mreg act as a negative immunoregulatory in transplantation.•Mreg combined with low-dose immunosuppressants may induce transplant immune tolerance.