A recent study with L. sigmodontis infections comparing IL-4Rα−/− with IL-4Rα−/−IL-5−/− combined deficiency also recorded residual eosinophilia in IL-4Rα–deficient mice, which was ablated when compound IL-5 deficiency was introduced and was significantly related to increased susceptibility to fecund adult infections (19). The gene discussed is IL5; the disease is infection.