Intercellular Adhesion Molecule 1 (ICAM1) 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 (TNFα) and is expressed by the vascular endothelium, macrophages, and lymphocytes. ICAM-1 is a ligand for LFA-1 (integrin), a receptor found on leukocytes.As ICAM1 has the function of cell adhesion, we measure the activity of ICAM1 by the ability of the immobilized protein to support the adhesion of PMA-stimulated MOLT4 human acute lymphoblastic leukemia cells.. When 1 x 106?cells/well are added to Recombinant Human ICAM1/CD54 coated plates (1.25 μg/mL with 100?μL/well), >10% cells will adhere after 2 hour incubation at 37 °C.The adhesion of MOLT4 after 2?hour incubation at 37℃ observed by inverted microscope was shown in Figure 1.