The blood-brain barrier in psychoneuroimmunology

The very term "psychoneuroimmunology" connotes separate compartments that interact. The BBB is the physical and physiologic dividing line between the immune system and the CNS and is the locale for interaction. Interactions between the immune system and the CNS are mediated at the BBB through a variety of mechanisms. The BBB restricts unregulated mixing of the immune substances in the blood with those in the CNS, directly transports neuroimmune active substances between the blood and the CNS, and secretes neuroimmune substances. All these normal functions of the BBB can be altered in an adaptive or pathologic manner by neuroimmune events. As such, the BBB is an important conduit in the communication of the immune and the central nervous systems.