TNF and Alzheimer disease: For the underlying mechanisms of FMT in the treatment of AD, FMT is reported to modulate the abundance of gut microbiota, the levels of SCFAs, and the immune balance of Th1/Th2 cells in AD mice, mainly manifested as downregulation of Th2 cytokines (IL-4, IL-5, and IL-13) and Treg cytokines (IL-10 and IL-1β), upregulation of Th1 cytokines (IL-12, IFN-γ, and TNF-α), as well as elevation of butyrate, propionate, and acetate [91].