The monoclonal HM.2 antibody reacts with the 90 kD glycoprotein Intracellular Adhesion Molecule-1 (ICAM-1). The adhesion molecule ICAM-1 belongs to the immunoglobulin superfamily, C2 subset; it is a ligand for the Integrins LFA-1 and MAC-1 and for CD43.ICAM-1 is an essential component in many immune-related processes. ICAM-1 links with receptors of the integrin family, thereby mediating cell-cell interactions and allowing for signal transduction. ICAM-1 interacts specifically with its receptors to induce a reversible adhesion interaction. For processes like T cell activation and leucocyte recruitment, normal immune function relies on ICAM-1. Therefore, it is understandable that alterations in ICAM-1 structure or expression are associated with immune disorders. It is important to properly understand the various functions and regulatory mechanisms of ICAM-1, the resulting disease-related failures, and the various treatments.ICAM-1 is a type of intercellular adhesion molecule continuously present in low concentrations in the membranes of leukocytes and endothelial cells. Upon cytokine stimulation, the concentrations greatly increase. ICAM-1 can be induced by interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha) and is expressed by the vascular endothelium, macrophages and lymphocytes