IL2 and neoplasm: To test if excess IL2 administered in vivo is capable of reversing the instability phenotype of Tregs from FS120m-treated mice, we treated tumor-bearing Foxp3EGFP-Cre-ERT2Rosa23flSTOPfl-tdRFP mice with FS120m or isotype control, then treated half of each group with a stabilised IL2:anti-IL-2 complex (rIL2 combined with an anti-IL2 mAb to increase half-life in vivo; ref. 55) on the last 3 days before analysis (Fig. 3C).