IL13 and Alzheimer disease: The concentrations of Th2 cytokines (IL-4, IL-5, and IL-13), which are known to contribute to the development of AD, were significantly decreased in the FMT_8w group compared with the before_FMT group, whereas the concentrations of Th1 cytokines, such as IL-12, IFN-γ, and TNF-α, were significantly increased (Fig. 4).