CD18, also known as integrin beta-2 (β2). CD18 is a subunit common to several leukocyte-specific integrin heterodimers, most notably Lymphocyte Function-Associated Antigen-1 (LFA-1, αLβ2) and Macrophage-1 Antigen (Mac-1, αMβ2). These integrins are expressed on all leukocytes and play a fundamental role in the inflammatory response. Under inflammatory conditions, endothelial cells upregulate adhesion molecules like Intercellular Adhesion Molecule-1 (ICAM-1).