Cerebral cell adhesion molecule: a novel leukocyte adhesion determinant on blood-brain barrier capillary endothelium.

The tight junctions of the cerebral capillary endothelium form the highly restrictive blood-brain barrier. Migration of leukocytes across this unique barrier may involve ligation of elements in addition to those of the fenestrated capillaries of the peripheral vascular system. An antibody raised against a bacterial adhesive protein and shown to have cross-reactivity with brain capillaries and to block leukocyte migration into the brain was used to identify and clone a novel determinant on brain microvessels. This cDNA was sequenced, and the expressed protein supported leukocyte adhesion in a CD18-dependent fashion. The high level of brain microvessel expression of this adhesion molecule, termed the cerebral cell adhesion molecule, implicates it in leukocyte transmigration across the blood-brain barrier.