Lymphocyte recruitment to the central nervous system (CNS) is a critical step in 
the pathogenesis of diseases such as multiple sclerosis (MS), meningitis and 
posterior uveitis. The principle sequential stages that control lymphocyte 
emigration from the blood have been widely reported, but only recently has 
attention been directed towards the role of the vascular endothelium in actively 
supporting transvascular migration. It has now been shown that adhesion 
molecules, particularly those of the immunoglobulin super family (e.g. ICAM-1, 
VCAM-1 and PECAM-1), not only act as ligands for leucocyte receptors but can 
also serve as signal transducers. Engagement of these receptors initiates 
endothelial signalling cascades that result in downstream effector mechanisms 
which in turn influence the progression of neuroinflammation. In particular, it 
has been shown that ICAM-1-mediated signalling in brain endothelial cells is a 
crucial regulatory step in the process of lymphocyte migration through the 
blood-brain barrier and as such represents an additional phase in the multistep 
paradigm of leucocyte recruitment. In this article we review current 
understanding of endothelial cell ICAM-1 signalling and discuss the importance 
of these findings in relation to leucocyte trafficking to the CNS.