Dissecting the modes of interactions amongst cell adhesion molecules

The process of cell adhesion can be mediated by more than 50 molecules. Fortunately, most of these can be grouped into a small number of superfamilies. For example, more than half of all leukocyte adhesion molecules are members of the immunoglobulin superfamily. The principles of cell-cell adhesion are reviewed including: kinetics and equilibria; on/off rates; affinities/avidities; homotypic/heterotypic interactions; mapping and delineation of binding sites. These principles are illustrated with two CAMs: firstly the interaction of the homotypic epithelial/myeloid adhesins CD66, and the endothelial adhesin, CD31, and secondly the heterotypic adhesins ICAM-1, 2 and 3, which interact with the leukocyte integrin LFA-1.