IL17A and allergic disease: In the traditional view, three basic lines are defined: type 1 immunity against intracellular pathogens (TH1 defense, viruses and intracellular bacteria, production of the IFN-γ cytokine and inflammation/autoimmunity); type 2 immunity against multicellular systems (TH2 defense, production of IL-4 and IL-5 cytokines and allergy/asthma) and type 3 immunity against extracellular pathogens (TH17 defense, bacteria and fungi, the production of IL-22 and IL-17 cytokines and inflammation/autoimmunity) [28].