Roles in Innate Immunity.

Microglia are best known as the resident phagocytes of the central nervous system (CNS). As a resident brain immune cell population, microglia play key roles during the initiation, propagation, and resolution of inflammation. The discovery of resident adaptive immune cells in the CNS has unveiled a relationship between microglia and adaptive immune cells for CNS immune-surveillance during health and disease. The interaction of microglia with elements of the peripheral immune system and other CNS resident cells mediates a fine balance between neuroprotection and tissue damage. In this chapter, we highlight the innate immune properties of microglia, with a focus on how pattern recognition receptors, inflammatory signaling cascades, phagocytosis, and the interaction between microglia and adaptive immune cells regulate events that initiate an inflammatory or neuroprotective response within the CNS that modulates immune-mediated disease exacerbation or resolution.