The aim of the study is to assess whether multiple infusions of donor-derived purified T regulatory cells (T reg DLI) in patients with steroid-refractory chronic GVHD is safe and whether it may induce clinical remission of GVHD. Based on the observation of the pathophysiological involvement of T regulatory cells in chronic GVHD, the adoptive transfer of donor T regulatory cells appears more reproducible and effective than their in vivo expansion following the administration of drugs.