The term activation is an oversimplification of a range of different ‘activated’ states. It is now recognized that activated microglia can exist broadly in two different states [6]. The first is classical activation, which is typified by the production of inflammatory cytokines and reactive oxygen species, while the second is a state of alternative activation, in which microglia take on an anti-inflammatory phenotype involved in wound repair and debris clearance [7]. It stands to reason that during neurodegenerative disease, where neuroinflammation is a prominent feature and potential contributor to disease, these alternatively activated microglia would be beneficial in resolving pathology.
