ABSTRACT
This chapter considers the factors which are believed to govern lymphocyte migration across the blood-brain barrier (BBB) and lead to central nervous system demyelination. Based on the premise that the initiation and progression of demyelination is dependent upon the activity of infiltrating blood lymphocytes, it addresses the question of whether migration across the BBB is a feature of a particular subpopulation of lymphocytes. Inflammation often arises from the untoward activity of blood leucocytes whose extravasation into tissue depends upon attachment to endothelial cells, passage across vessel walls, and migration along a chemotactic gradient. The term selectin was introduced to describe several adhesion molecules whose function and expression were highly selective and which possessed a terminal lectin domain. If demyelination is dependent upon the activity of infiltrating CD4-positive lymphocytes then abrogating their passage across the BBB should produce disease amelioration. Antagonising the expression of adhesion molecules is another means of impeding lymphocyte migration across the BBB.
