Front Matter

Luminal

membrane

Blood Hg

Endothelial cell

Abluminal

membrane

Luminal

membrane

Blood Hg

Endothelial cell

Tight junction

Astrocyte

Basement

membrane

Pericyte

Astrocyte

Neuron

Brain
capillary

Abluminal

membrane

Tight junction

Astrocyte

Inammatory cytokines

Mercury in vaccines/

Environmental

chemicals

Leaky BBB

Basement

membrane

Pericyte

Astrocyte

Neuron

Brain
capillary

(a)

(b)

Figure 9.1 The blood–brain barrier (BBB) is a highly selective semipermeable membrane
barrier that separates the circulating blood from the brain extracellular fluid in the CNS.
The BBB is formed by brain endothelial cells, which are connected by tight junctions.
(a) A normal BBB. (b) A leaky BBB, induced by inflammatory cytokines, particularly
interleukin 6 (IL‐6).