IL-2/S4B6 has been shown to induce potent stimulatory activity of NK cells as well as memory and activated CD8+ T cells, and since the complex has demonstrated antitumor activity in several mouse tumor models, it has been established for more than a decade that these CD25-blocking IL-2cx are suitable for cancer immunotherapy.2 15 Meanwhile, the CD25-biased IL-2/JES6 has been shown to extensively expand Treg cells and has been effective in preclinical models of autoimmune disease2 19 and transplantation.20 This evidence concerns the gene IL2 and neoplasm.