ICAM-1 is also known as CD54. This adhesion molecule, expressed at the surfaces of immune system and endothelial cells, is up-regulated by cytokine stimulation. ICAM-1 has 5 Ig-like domains, a transmembrane region and a small carboxyl-terminal cytoplasmic domain. ICAM1 bind two integrin: leukocyte function associated antigen (LFA1 and CD11a/CD18) and macrophage 1 antigen (Mac-1, CD11b/CD18) (Bella et al., 1998; Yang et al., 2004).
The extracellular domain of ICAM-1 can be detected in serum of healthy controls and levels are increased under disease. Serum ICAM-1 has been proposed as an indicator of inflammatory disease as soon as 1991 (Rothlein et al., 1991). The mechanism leading to the release of ICAM-1 is not fully understood and there is probably a shedding by membrane protease and an alternative RNA splicing (Witkowska and Borawska, 2004). It is possible that ADAM17 participate in the shedding of ICAM1 (in vitro studies) (Tsakadze et al., 2006).
SICAM-1 assay is a solid phase enzyme linked immunoassay which has been validated in the laboratory for measurement in human serum. The kit measures only the wild type allele of ICAM-1 and does not recognize ICAM-1 with the Kilifi mutation.
Bella, J., Kolatkar, P.R., Marlor, C.W., Greve, J.M., and Rossmann, M.G. (1998). The structure of the two amino-terminal domains of human ICAM-1 suggests how it functions as a rhinovirus receptor and as an LFA-1 integrin ligand. Proc. Natl. Acad. Sci. U. S. A. 95, 4140–4145.
Rothlein, R., Mainolfi, E.A., Czajkowski, M., and Marlin, S.D. (1991). A form of circulating ICAM-1 in human serum. J. Immunol. 147, 3788–3793.
Tsakadze, N.L., Sithu, S.D., Sen, U., English, W.R., Murphy, G., and D’Souza, S.E. (2006). Tumor Necrosis Factor-α-converting Enzyme (TACE/ADAM-17) Mediates the Ectodomain Cleavage of Intercellular Adhesion Molecule-1 (ICAM-1). J. Biol. Chem. 281, 3157–3164.
Yang, Y., Jun, C.-D., Liu, J., Zhang, R., Joachimiak, A., Springer, T.A., and Wang, J. (2004). Structural Basis for Dimerization of ICAM-1 on the Cell Surface. Mol. Cell 14, 269–276.