T-cell-mediated immune responses during filariasis depend on the phase of the infection: (1) the acute phase is characterized by skewed Th2 response (with enhanced secretion of IL-4, IL-5, and IL-13); (2) the chronic phase is associated with “modified Th2 response” with Tregs (with enhanced IL-10 and TGF-β secretion) playing a major role compared to Th2 cells; and (3) the chronic pathology phase is characterized by a shift towards “Th1/Th17” (enhanced secretion of IFN-γ, IL-2, and IL-17) response, which takes place in individuals who develop pathology (45). This evidence concerns the gene IL4 and infection.