IL4 and Alzheimer disease: Th2 lymphocytes play a prominent role in the initiation and progression of allergic disease, including asthma and AD, by releasing IL-4, IL-5, and IL-13, which promote IgE-mediated allergic inflammation, and IFN-γ, a Th1 cytokine secreted by Th1 cells, acts in conjunction with Th2 cytokines in maintaining the chronic inflammatory response in allergic disease, particularly in asthmatic airways (Ngoc et al., 2005).