Clone MR106 recognizes the CD106 antigen, a 110 kDa transmembrane protein also known as vascular cell adhesion protein 1 (VCAM-1). CD106 is expressed on bone marrow stromal cells, myeloid cells, and dendritic cells, but not on peripheral leukocytes. Expression on endothelial cells is upregulated upon inflammatory cytokine stimulation. CD106 is an endothelial ligand for the very late antigen-4 (VLA-4 or α4β1) of the β1 subfamily of integrins, and for integrin α4β7. It mediates the adhesion of lymphocytes, monocytes, eosinophils, and basophils to vascular endothelium. CD106 also functions in leukocyte-endothelial cell signal transduction, and it may play a role in the development of atherosclerosis and rheumatoid arthritis.