Fig. 2

Microglial function and AD pathology. Microglia are present throughout the brain and their distribution varies by region. They have different shapes that reflect their essential functions of maintaining cerebral homeostasis and defense. Ramified microglia are the most common type in the healthy brain. They use branches to monitor the cerebral environment and detect injury signals. They then move their branches toward the damaged site and trigger a microglial response that involves reshaping synapses and keeping myelin stable. Microglia become highly ramified and have a robust power to clear pathogens. The highly branched form of microglia can also transform into a less branched shape as a result of engulfing pathological items, such as Aβ and Tau proteins. Microglia become dystrophic and hyperinflammatory with aging and neurodegenerative disorders such as AD. Moreover, the morphology of microglia varies in different regions and stages of the diseased brain. The temporal changes of the microglia aspect could depend on the intensity and duration of exposure to the harmful environment but could also be attributed to the divergent reaction of microglia to differing substances like Aβ or tau. AD, Alzheimer’s disease; Aβ, amyloid beta; PAMPs, Pathogen-associated molecular patterns