The main cause of AD is not fully delineated, and we and others have shown that the onset of AD seems to be more accurately caused by an imbalance between type-1 and type-2 helper T cells (Th1/Th2) in the immune system, and the factors induce Th2 cells to produce Th2 cytokines such as interleukin (IL)-4, IL-5, IL-10, and IL-13 and high IgE levels. Here, IL13 is linked to Alzheimer disease.