Very interestingly, because it suggests that fish TH2 responses are involved in anti-parasite immunity, the infection of salmon with the parasite Paramoeba perurans enhanced the expression in infected gill of TH2 signature genes IL-4/13A and IL-4/13B while the expression of signature genes for TH1, TH17 and Treg like IFNG, IL-17A/F, TGFB1 and IL-10 were downregulated [246]. This evidence concerns the gene IL17A and infection.