FOXP3 and infection: After secondary infection of Il4rafl/fl mice (Fig. 6 D), the proportion and absolute number of ex-Foxp3 Th2 cells were significantly reduced compared with Hp 2° Il4rawt/wt mice (Fig. 6, E–G), demonstrating a fundamental requirement for IL-4 signaling in Foxp3-expressing cells for the development of ex-Foxp3 Th2 cells.