CD146?(cluster?of?differentiation?146), also known as MUC18 or MCAM, is a putative adhesion molecule that belongs to the immunoglobulin superfamily (IgSF). It is an approximately 113-kDa type1 transmembrane glycoprotein that?is?expressed?at the intercellular junction of endothelial cells. CD146 was originally identified as a tumor marker for melanoma (MCAM) due to its existence only in melanoma but not in the corresponding normal counterpart. However CD146 is not just a CAM for the inter-cellular and cell-matrix adhesion. Recent evidence indicates that CD146 is actively involved in miscellaneous processes, such as development, signaling transduction, cell migration, mesenchymal stem cells differentiation, angiogenesis and immune response. CD146? and PECAM-1 are both members of immunoglobulin superfamily of cell adhesion molecules. PECAM-1 has been identified as an interactor of CD146, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human CD146 and recombinant rat PECAM-1. Briefly, CD146 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to PECAM-1-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-CD146 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 ul stop solution to the wells and read at 450/630 nm immediately. The binding activity of recombinant human CD146 and recombinant rat PECAM-1 was shown in Figure 1, the EC50?for this effect is 3.6 ug/mL.