While Kopf et al. and Mohrs et al. demonstrated that IL-4−/− and IL-4Rα−/− mice were able to control CL (7, 9) (Figure 3), Noben-Trauth et al. showed that IL-4−/−- and IL-4Rα−/−-deficient BALB/c mice remained susceptible to disease and could not contain parasites at the site of infection (37, 91). This evidence concerns the gene IL4 and infection.