Over an eight-week period, IL-2 therapy induced a series of changes in Treg homeostasis including increased proliferation and thymic export and an enhanced resistance to apoptosis.23 Similarly, low-dose IL-2 administration has been tested in patients receiving hematopoietic stem cell transplantation in order to prevent GVHD.24 No adverse events of grade 3 or 4 nor any induction of GVHD were reported. The gene discussed is IL2; the disease is graft versus host disease.