IL4R and infection: Because immune resistance to filarial infection is dependent on a sustained influx of eosinophils mediated by the CCR3-CCR3 ligand chemokine pathway (1, 4, 11, 18, 21), the levels of Siglec F+ eosinophils in the peritoneal infection site were compared between WT, IL-4Rα−/−, and CCR3−/− mice (Fig. 2A, 2B).