FOXP3 and infection: Interestingly, earlier in the course of infection (day 5 p.i.), there was no such reduction in lung Treg cells in the mutant; and if anything, there was a trend toward augmented Treg cells in mutants at this earlier phase (corresponding FOXP3 + T cell graphs in Fig. 3B, and Fig. 3C, right), which may also be important for anti-viral germinal center responses25,27.