Similar microfilaremias were recorded between WT and IL-4Rα−/−, IL-4Rα−/−CCR3−/−, or IL-4Rα−/−IL-5−/− mice, indicating that these immunodeficiencies did not have any impact on mf parasitism in the blood during the first 4 wk of a primary infection. The gene discussed is IL4R; the disease is infection.