Studies in vasculitis, graft‐versus‐host disease, systemic lupus erythematosus and type 1 diabetes suggest that an IL‐2 dose range of 0·3–3·0 × 106 IU/m2 is well tolerated, and achieves a preferential increase in the percentage of Treg with no induction of effector T cell activation 23, 25, 33, 34. The gene discussed is IL2; the disease is type 1 diabetes mellitus.