CD28 and influenza: 12 days after influenza infection, the proportion of Th1-type Tregs cells was reduced in the medLN (Figure 8G,H) and lung (Figure 8I), likewise the proportion of T follicular regulatory cells in the medLN was reduced in Cd28flox/floxOx40cre/+ mice (Figure 8J,K), consistent with the lack of T follicular regulatory cells in CD28-deficient mice (Linterman et al., 2011; Sage et al., 2013).