Microglial Function in MS Pathology

In the quiescent state, ramified microglia are responsible for routine immune surveillance within the central nervous system. In response to injury or insult, microglia become activated and undergo morphological change to a hyper-ramified, activated or amoeboid morphology (Streit et al., Prog Neurobiol 57(6):563–581, 1999; see Fig. 3.1). It has long been held that microglial activation is deleterious during MS lesion evolution. However, more recently, beneficial roles have also been ascribed to microglia during MS pathogenesis with evidence gleaned predominantly from animal models. In this chapter, microglial function in the context of MS will be discussed with evidence drawn from both human pathology and animal models. Microglial phagocytic activity, remodelling, inflammation, immunomodulation and repair will be examined and the molecular mechanisms that are posited to underpin these disparate roles critiqued.