A direct requirement for IL-4/IL-13 signaling in worm expulsion is demonstrated by IL-4 receptor antibody blocking experiments, and in IL-4R−/− and STAT6−/− mice, dramatically limiting worm expulsion during T. muris (7), Heligmosomoides polygyrus (10) or N. brasiliensis (11) infection. The gene discussed is IL4; the disease is infection.