To determine the role that the IL-4/IL13 receptor plays in the development of alternatively activated macrophages (AAM or M2) and their role in the regulation of immunity to the extraintestinal phase of the helminth parasite Taenia crassiceps, we followed the infection in a mouse strain lacking the IL-4Rα gene (IL-4Rα−/−) and in the macrophage/neutrophil-specific IL-4Rα-deficient mouse strain (LysMcreIL-4Rα−/lox or cre/LoxP). The gene discussed is IL4R; the disease is infection.