IL4 and infection: To resist infections by intracellular pathogens such as CLA, immune responses of the Th1 type dominated by the production of cytokines of the type IL-2, IFN-γ, TNF-α, as well as production of antibodies of the IgG2a subtype, are required, while protection from infections by extracellular pathogens is often associated with humoral immune responses dominated by the production of IgG1, IL-4, and IL-10 [29].