IL4 and allergic disease: Among these, there are Th1 cells (proinflammatory cells with a critical role in defense against intracellular pathogens, producing IFN-γ, IL-2, TNFα), Th2 (involved in allergic diseases and response against parasites, producing IL-4, IL-5, IL-13, IL10), Th17 (proinflammatory cells with a defensive role against extracellular bacteria, but also fungi, producing IL17A, IL17F, IL21, IL22, IL23), Th22 (antibacterial functions, producing IL-22), Treg (key elements in the maintenance of self-tolerance, suppressing T-cell activation and releasing IL-10, TGF-β, IL-4) (220).