However, chronically activated microglia continually secrete pro-inflammatory cytokines (e.g., TNFα, IL-6, IL-1α, and GM-CSF), which is an important, albeit harmful, aspect of neuroinflammation evident in the AD brain, leading to a sustained pro-inflammatory environment as well as suppression of neuronal activity and injury of bystander neurons [220]. This evidence concerns the gene TNF and Alzheimer disease.