IL13 and infection: Surprisingly, while there was no statistical difference between IL-33−/− mice and WT mice in terms of the production of IL-5 in spleens during the course of infection (U = 19, P = 0.1949; U = 8, P > 0.999; U = 2, P = 0.8 at 6, 9 and 12 wpi, respectively; Fig. 2c), there was a statistically significant difference in the production of IL-13 at the sixth week of infection (t(8) = 2.39, P = 0.042; Fig. 2d).