Meanwhile, a regulated, antigen-specific Th2 response is most often associated with long-lived, asymptomatic parasite survival [48,50,51]; in such an outcome, regulatory T cells and basophils are associated with host tolerance to infection while interleukin 4 (IL-4)-producing eosinophils and basophils maintain Th2 polarization [52,53,54,55]. This evidence concerns the gene IL4 and infection.