IL4 and infection: This effect is perhaps best demonstrated during the infection of the nematode Trichuris muris where Interleukin-4 (IL-4) and IL-13 mediated Th2 responses lead to rapid expulsion in resistant mouse strains, whereas susceptible mouse strains produce high levels of Interferon-gamma (IFN-γ), IL-12 and IL-18, which are characteristic of a predominant Th1 response (5, 6).