ICAM-1 (Intercellular Adhesion Molecule 1), also known as CD54, is a transmembrane glycoprotein of 532 amino acids, with a molecular weight of 75 to 115 kD. ICAM-1 is expressed on endothelial cells and many cells of the immune system, such as macrophages and lymphocytes. ICAM-1 is also expressed by respiratory epithelial cells and is the binding site for rhinovirus. ICAM-1 expression can be induced by interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-alpha). ICAM-1 binds to two beta 2 family integrins, CD11a/CD18 (LFA-1) and CD11b/CD18 (Mac-1), on the surface of leukocytes. ICAM-1/LFA-1 interaction is the key event for recruiting immune cells to the periphery at sites of infection or inflammation. Besides its classically described functions as an adhesion and viral entry molecule, ICAM-1 also plays a role in signal transduction. The signal-transducing functions of ICAM-1 seem to be associated primarily with proinflammatory pathways. In particular, ICAM-1 signaling seems to produce a recruitment of inflammatory immune cells such as macrophages and granulocytes. ICAM-1 ligation also prolongs antigen presentation by dendritic cells and promotes T cell proliferation and cytokine release. Besides its role in immune responses, ICAM-1 also participates in angiogenesis, wound healing, and bone metabolism. Soluble forms of ICAM-1 (sICAM-1) have been identified in culture supernatant, blood, cerebrospinal fluid, and bronchoalveolar lavage fluid. Soluble ICAM-1 is generated by shedding from the cell surface (cleavage by multiple forms of metalloproteinases and/or TACE/ADAM17). Elevated levels of sICAM-1 are associated with various disease conditions including diabetes, cardiovascular disease, organ transplant rejection, hypertension, liver disease, and cancer. Soluble ICAM-1 is becoming an important disease biomarker. BioLegend's LEGEND MAX(TM) Human sICAM-1/CD54 ELISA Kit is a Sandwich Enzyme-Linked Immunosorbent Assay (ELISA) with a 96-well strip plate that is pre-coated with a capture antibody. This kit specifically quantitates human sICAM-1 from cell culture supernatant, serum, plasma, and other biological fluids. It is analytically validated with ready-to-use reagents.