The association of IgG4 with severe forms of schistosomiasis has been justified by the increased susceptibility of the host to infection with the parasite; this finding indicates that an excess of IgG4 would block the protective effect of IgE, favoring parasite establishment and increasing egg deposition into host tissue and the progression to severe forms of the disease [26], [57], [58]. This evidence concerns the gene IGHE and infection.