Figure 2.

Increased periphery inflammation leads to disruption of the blood–brain barrier (BBB). (A) In healthy BBB, tight junctions between brain endothelial cells form the primary physical barrier that prevents the entry of large and potentially toxic molecules into the brain. Endothelial cells are encompassed by basal lamina, pericytes, and astrocytic endfeet. Pericytes and astrocytic endfeet interact closely with the endothelial cells and can help maintain BBB integrity. (B) Inflammation, caused by an infection or virus, can lead to immune cell infiltration. Increased periphery inflammation has a detrimental effect on the integrity of the BBB at various levels, including endothelial cell degradation or shrinkage, altered paracellular transport pathways via loss of tight junction proteins, as well as dysfunction of pericytes and astrocytes. Loss of BBB integrity makes it more permeable, allowing immune cells and inflammatory cytokines to enter the brain parenchyma, which in turn leads to microglial activation to induce neuroinflammation. Neurons may experience demyelination or become damaged.