The administration of low-dose IL-2 has been used in autoimmune conditions such as graft versus host disease, autoimmune vasculitis, hepatitis, type 1 diabetes mellitus and systemic lupus erythematosus, to boost Treg numbers with promising results.17 21–24 Furthermore, a recent study involving patients with 11 autoimmune conditions demonstrated the clinical efficacy and safety of low-dose IL-2.25 Here, IL2 is linked to graft versus host disease.