TGFB1 and acute graft versus host disease: As a well‐characterized immunosuppressive molecule, it can down‐regulate multiple immune responses and participate in the pathological process of immune disorders.21 TGF‐β1 can be secreted by MSC and plays a non‐redundant role in the immunomodulatory function of MSC.22, 23 Sławomira KyrczKrzemień showed that low level of TGF‐β1 probably being one of the factors contributing to the development of acute GVHD.