The endothelium is the thin layer of cells that lines the interior surface of blood vessels forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells.
Platelet endothelial cell adhesion molecule (PECAM-1) is an antigen, which is typically shared by both endothelial and distinct hematopoietic cells. It is widely expressed among leukocytes and functions as a cell adhesion molecule.