The R6-5-D6 monoclonal antibody reacts with human CD54 also known as Intercellular Adhesion Molecule-1 (ICAM-1), is a single-chain transmembrane glycoprotein with a polypeptide core of 55 kDa and a member of the Ig superfamily. CD54 is typically expressed on non-hematopoietic cells such as endothelial cells, thymic epithelial cells, and fibroblasts but can also be expressed on macrophages, T-lymphoblasts, germinal center B cells and dendritic cells. CD54 is a ligand for LFA-1, a receptor found on leukocytes. When activated, leukocytes bind to endothelial cells via CD54/LFA-1 and then transmigrate into tissues. Pro-inflammatory cytokines such as IL-1, TNF and IFNγ induce CD54 expression on endothelial cells and fibroblasts. The R6-5-D6 antibody has been reported to inhibit the interaction of CD54 with leukocytes, thereby decreasing leukocyte adhesion to the vascular endothelium and inflammatory tissue injury.