IL2 and systemic lupus erythematosus: The reduced frequencies of CD25hi Treg and the Treg/Tcon proliferation imbalance, which both correlated with disease activity, are typical indicators of a low availability of IL-2 and constitute the most relevant defects in Treg biology in SLE, which, however, can be corrected by treatment with low doses of IL-2 (17, 19, 21).