IL6 and graft versus host disease: IL-6, which induces TGF-β dependent differentiation of Th17 but not Treg cells, was found to play a relevant role in GVHD induction, as blocking of the IL-6R led to reduced GVHD pathology and Th1/Th17 cells in GVHD target organs, while absolute numbers of Tregs increased (145).