Th2 cytokines, such as IL-4, IL-5, IL-6, IL-10, IL-13, IL-25, and IL-31, are involved in the acute phase of AD; Th1 cytokines, such as IL-2, IL-12, IL-18, and IFN-γ, are involved in the chronic inflammatory stage. Here, IL31 is linked to Alzheimer disease.