IL7 and infection: While TSLPR−/− mice showed similar weight loss compared to WT mice, both IL-7Rα449F and Dmu mice lost significantly more weight from day 7 post-infection onwards compared to WT (Fig. 1a) suggesting that IL-7, not TSLP, was critical for protection from influenza A. We then determined whether the weight loss seen was due to a failure to clear the virus by examining the levels of infectious virus in the lungs of mice nine days after infection.