IgG2a, IL-2, TNF-α, and IFN-γ are related to Th1 immune response which is effective for protection against intracellular infections [54], while the Th2 immune response is required for protective immunity against extracellular infections such as parasitic infections, including those caused by helminths, and characterized by the production of IL-4, IL-5, IL-6, and IL-10 cytokines and IgG1 [55, 56]. This evidence concerns the gene IL2 and parasitic infectious disease.