Immune System in Central Nervous System

Although central nervous system (CNS) has long been known as an immune privileged site, in common with all other tissues, it requires effective immune mechanisms to protect against infections. More recent data support that certain areas of healthy CNS are continuously monitored by resident microglia and blood-borne immune cells such as macrophage and T-cell to sustain CNS immune surveillance. Interruption of CNS surveillance by lymphocyte traffic inhibition results in injury and infection by viruses such as JC virus, herpes simplex virus, etc. CNS Immune system has to be regulated in a unique way in order to prevent inflammation and autoimmune reactions against CNS derived antigens, which there is no tolerance for them.
Here, we discuss the anatomical and cellular aspects of immune surveillance in the CNS. Moreover, we review a new model to explain how antigen-specific T-cell responses occur in the CNS.