Similar to IL-4−/− neonates (Figure 4B), IL-4Rα−/− neonates had significantly less arginase activity within the lung following P. murina infection as compared to wild type neonates, confirming that the ability of macrophages to respond to IL-4 is essential in driving arginase activity during the immune response to infection (Figure 7A). This evidence concerns the gene IL4 and infection.