T cell extravasation into perivascular tissue during inflammation involves transient adhesion to the blood vessel endothelium, followed by transmigration across the endothelial cell layer and establishment of residency at the inflammatory site. Transmigrating T cells presumably utilize enzymes known as matrix metal metalloproteinases (MMPs) to make selective clips in the extracellular matrix components of the subendothelial basement membrane en route to perivascular tissues. This process is part of normal, protective immune responses, but may also be pathological in the case of autoimmune diseases, such as experimental autoimmune encephalomyelitis (EAE).