Rapid

induction of clinical remission by low-dose interleukin-2 in a patient with refractory SLE Interleukin-2 (IL-2) is crucial for the growth and survival of regulatory T cells (Treg) and, thus, for the control of auto-immunity.1 2 In previous studies, we have proven a causal rela-tionship between an acquired IL-2-deficiency, defects in Treg biology and the development of systemic lupus erythematosus (SLE).3 Accordingly, we showed that compensation of IL-2 defi-ciency by IL-2 therapy corrects associated Treg defects and ame-liorates already established disease in lupus-prone mice.3 In line with this, two independent clinical studies showed recently that low-dose IL-2 induced expansion of the Treg pool and reduced clinical symptoms in two different immunological diseases without known IL-2 deficiency.4 5 These promising clinical find