Untreated Giardia-infection may regulate innate and adaptive immune responses mediated by Th17 CD4+T cells and induction of Th1, Th2 and Th17 cytokines, including IL-2, IL-5, IL-6, IL-8, IL-12, IL-13, IL-23, IFN-γ and TNF-α [37, 38]. This evidence concerns the gene IL5 and giardiasis.