Type-I T cells produced type-I cytokines, such as IL-2, TNF-α, and IFN-γ, to enhance cellular response to remove infected cells, whereas Type-II T cells produced type II cytokines, such as IL-4, IL-5, and IL-10, to increase antibodies to attack exogenous antigen to prevent host-cell infection [21]. The gene discussed is IL4; the disease is infection.