Intercellular Adhesion Molecule 1 (ICAM-1), also known as CD54, is a nearly ubiquitous transmembrane glycoprotein that plays a key role in leukocyte migration and activation . Human ICAM-1 contains five Ig-like domains in its extracellular domain (ECD) and associates into non-covalently linked dimers. Soluble forms of monomeric and dimeric ICAM-1 (sICAM-1) can be generated via proteolytic cleavage by cathepsin G, elastase, MMP-9, MMP-14/MT1-MMP, and TACE/ADAM17. In the mouse, alternate splicing generates isoforms that lack particular Ig-like domains and are differentially sensitive to proteolysis. Within the ECD, human ICAM-1 shares 53% amino acid sequence identity with mouse and rat ICAM-1.

The principal binding partners of ICAM-1 are the leukocyte integrins LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18). The multivalency of dimeric ICAM-1 increases its strength of interaction with LFA-1. ICAM-1 also binds several non-integrin ligands including CD43/sialophorin, fibrinogen, hyaluronan, rhinoviruses, and Plasmodium falciparum-infected erythrocytes. At sites of inflammation, ICAM-1 is upregulated on endothelial and epithelial cells where it mediates the adhesion and paracellular migration of leukocytes expressing activated LFA-1 and Mac-1. ICAM-1 ligation prolongs antigen presentation by dendritic cells and promotes T cell proliferation and cytokine release. ICAM-1 activation also participates in angiogenesis, wound healing, and bone metabolism .

Soluble ICAM-1 has been reported in serum, cerebrospinal fluid, urine, and bronchoalveolar lavage fluid . Elevated levels of sICAM-1 in these fluids are associated with cardiovascular disease, type 2 diabetes, organ transplant dysfunction, oxidant stress, abdominal fat mass, hypertension, liver disease, and certain malignancies. sICAM-1 promotes angiogenesis and serves as an indicator of vascular endothelial cell activation or damage. It also functions as an inhibitor of transmembrane ICAM-1 mediated activities such as monocyte adhesion to activated endothelial cells and sensitivity of tumor cells to NK cell-mediated lysis.

This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for sICAM-1 has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any sICAM-1 present is bound by the immobilized antibody. Following incubation unbound samples are removed during a wash step, and then a detection antibody specific for sICAM-1 is added to the wells and binds to the combination of capture antibody- sICAM-1 in sample. Following a wash to remove any unbound combination, and enzyme conjugate is added to the wells. Following incubation and wash steps a substrate is added. A coloured product is formed in proportion to the amount of sICAM-1 present in the sample. The reaction is terminated by addition of acid and absorbance is measured at 450nm. A standard curve is prepared from seven sICAM-1 standard dilutions and sICAM-1 sample concentration determined.

Figure 1:Schematic diagram of the assay

1. Aluminium pouches with a Microwell Plate coated with antibody to human sICAM-1 (812)

2. 2 vials human sICAM-1 Standard lyophilized, 4000 pg/ml upon reconstitution

3. 2 vials concentrated Biotin-Conjugate anti-human sICAM-1 antibody

4. 2 vials Streptavidin-HRP solution,

5. 4 bottle Standard /sample Diluent

6. 1 bottle Biotin-Conjugate antibody Diluent

7. 1 bottle Streptavidin-HRP Diluent

8. 1 bottle Wash Buffer Concentrate 20x (PBS with 1% Tween-20)

9. 1 vial Substrate Solution

10. 1 vial Stop Solution

11. 4 pieces Adhesive Films

12. package insert

NOTE: [96 Tests]

Unopened Kit：Store at 2 -8° C. Do not use past kit expiration date. opened/ReconstitutedReagents：Please refer to the datasheets for detail information.

1. Hogg, N. et al. (1991) Chem. Immunol. 50:98.

2. Witkowska, A.M. and M.H. Borawska (2004) Eur. Cytokine Netw. 15:91.

3. Staunton, D.E. et al. (1988) Cell 52:925.

4. Reilly, P.L. et al. (1995) J. Immunol. 155:529.

5. Robledo, O. et al. (2003) Eur. J. Immunol. 33:1351.

6. Sithu, S.D. et al. (2007) J. Biol. Chem. 282:25010.

7. Fiore, E. et al. (2002) Oncogene 21:5213.

8. Tsakadze, N.L. et al. (2006) J. Biol. Chem. 281:3157.

9. Jun, C.D. et al. (2001) Proc. Natl. Acad. Sci. 98:6830.