CD54, a member of the immunoglobulin superfamily of cell surface receptors and also known as Intercellular Adhesion Molecule-1 (ICAM-1), is a type I transmembrane glycoprotein that mediates important cell/cell interactions. CD54 is expressed on endothelial cells, dendritic cells, keratinocytes, and lymphocytes. Its expression is upregulated by inflammatory mediators such as IFN ?, IL-1, TNF-a, lipopolysaccharide, and phorbol esters. Endothelial CD54 contributes to the extravasation of leukocytes from blood vessels, particularly in areas of inflammation. CD54 on antigen-presenting cells contributes to antigen-specific T-cell activation, presumably by enhancing interactions between T cell and antigen-presenting cells. These adhesion reactions are mediated via the binding of CD54 to its major ligands, LFA-1 and Mac-1.