TNF and graft versus host disease: It was shown recently that TNF priming induces the proliferation and activation of Tregs in vivo via TNFR2 that prolongs animal survival when compared with unprimed Tregs in acute mouse GvHD model, and TNF–TNFR2 interaction represents a novel therapy to prevent GvHD after allogeneic hematopoietic stem cell transplantation (allo-HCT) (12, 13).