The blood-brain barriers

Abstract

The blood-brain barriers (BBBs) are mainly located at the levels of the vasculature, choroid plexus, and the circumventricular organs and play multiple roles in neuroimmunology. The ability of the BBBs to separate the blood and its contents from the central nervous system (CNS) is largely responsible for the CNS being an immune-privileged region. However, the BBB then revises this separation in a regulated way by a variety of mechanisms, including the ability to transport cytokines, regulate the entry of immune cells into the brain, and to itself secrete into the blood and into the CNS immunoactive substances. The BBB thereby participates in a number of neuroimmune axes that allow communication between the CNS and the peripheral immune cells. Failure of the highly regulated activities of the BBBs can be both a cause and consequence of immune diseases.