This antibody reacts with the CD146 antigen, which is expressed on melanoma cells, epithelial cells, endothelial cells, fibroblasts, activated T cells, multipotent mesenchymal stromal cells, and activated keratinocytes. CD146 mediates heterophilic cell adhesion and regulates monocyte transendothelial migration. The ligand of CD146 remains to be identified. Among peripheral whole blood leucocytes, CD146 expression is not detected, except on a subset of activated T-lymphocytes.