The role of carbohydrate in heterotypic cell-cell recognition: lymphocyte-high endothelial cell interaction as a...

The studies reviewed here demonstrate that the interaction of lymphocytes with HEV is one of the most approachable models available for the study of heterotypic cell-cell recognition mechanisms. Lymphocyte-HEV interaction is mediated by specific lymphocyte surface receptors recognizing, by as yet unknown mechanisms, determinants expressed by specialized high endothelial cells in lymphoid tissues and sites of chronic inflammation. Both the lymphocyte and endothelial cell surface elements of the interaction are precisely regulated, controlling the traffic of lymphocyte subsets through particular lymphoid organs and into sites of inflammation. Considerable progress, reviewed here, has been made in defining and characterizing the lymphocyte surface molecules mediating this cellular interaction. By contrast, the nature of the endothelial cell determinants recognized by migrating lymphocytes remains a mystery. Future experiments must be designed to identify these endothelial cell determinants, and to examine critically a proposed role of carbohydrate in lymphocyte-HEV interaction.