Endothelial cell interactions and integrins

Adhesion molecules on the endothelium and leukocytes are involved in mediating cell-cell adhesion, which is an initial step in the leukocyte migration response. These adhesion molecules, some of which are present constitutively and others that can be up-regulated in response to chemotactic and proinflammatory stimuli, regulate the trafficking of leukocytes across the vascular endothelial barrier. A basic mechanism of interaction between the endothelium and leukocytes involves CD11/CD18 integrins, which bind to members of the immunoglobulin super gene family-intercellular adhesion molecule (ICAM)-1 and ICAM-2. The interaction between CD11/CD18 integrins and ICAM-1 is required for leukocyte migration. The other important adhesive interaction between leukocytes and the endothelium involves binding of selectins to their endothelium carbohydrate counterreceptors on leukocytes. The selectin-mediated binding is involved in leukocyte "rolling," whereas CD11/CD18 integrins are responsible for strengthening and stabilizing the leukocyte adhesion. This review summarizes the current literature on leukocyte adhesion molecules, in particular, the endothelial cell interactions mediated by the CD11/CD18 integrins.