TGFB1 and graft versus host disease: In a number of different allogeneic HCT animal models, the addition of highly purified CD4+CD25+FoxP3+ Tregs resulted in suppression of GVHD.53 We hereby speculate that increased Treg cells might be involved in regulating immune response in aGVHD mice infused with MSC‐TGF‐β1.