IL21 and infection: To determine if increased Th1 bias in the stat3−/− Teff observed during the first infection was maintained into the memory phase, we analyzed antigen-experienced memory T cells (Tmem, CD11ahiCD49dhiCD44hiCD127hi) at day 55 p.i. Indeed, STAT3-deficient Tmem had higher percentages of IFN-γ+IL-21- Th1-like cells (Figure 7F) and maintained higher expression of T-bet (Figure 7G) than WT.