From the immunological point of view, the central nervous system (CNS) has special characteristics, for example, having a blood-brain barrier, which in the absence of an inflammatory process prevents the entry of cells from the immune system into the central nervous system.

In this system, the first line of immune defense is constituted by the microglia that belongs to the monocyte-macrophage system, the microglia is activated by the cells of the immune system, which after an inflammatory process, can cross the blood-brain barrier; when activated, they increase their phagocytic activity that leads to the production of cytokines that complete the inflammatory cascade.