The blood-brain barrier (BBB) is a complex and dynamic structure that protects the brain from cells within the vasculature, from the immune system and from pathogens. This barrier is present in arterioles, capillaries and venules and is formed at the level of adjacent endothelial cells, which are coupled to astrocytes, microglia, neurons and pericytes. The structure of this endothelial barrier is unique among endothelia of other organ systems and is composed of complexes made up of tight, gap and adherens junctions. In addition, it is the responsibility of the surrounding cellular elements to...