In a cohort of patients with chronic refractory GVHD, low dose IL-2 administration (0.3–1×106 IU/m2) increased Treg:Teff ratio, with improvement in clinical symptoms and enabling tapering of steroid dose by a mean of 60%.132 Similarly, low dose IL-2 (1–2×105 IU/m2) post-allogeneic SCT in children prevented acute GVHD when compared with those who did not receive low dose IL-2.133. Here, IL2 is linked to graft versus host disease.