TNF and Alzheimer disease: Increasing evidences suggest that microglia, the first line of defense and the resident macrophages of the brain in the central nervous system (CNS), play multiple roles in AD progression by clearing Aβ plaques and releasing pro-inflammatory mediators [e.g., tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β)], which might directly act on neurons to induce apoptosis (1, 4, 6, 7).