 It has been found on endothelial cells in all tissues, activated macrophages, activated monocytes, lymphoblasts fibroblasts, and smooth muscle cells.Endoglin was first identified using monoclonal antibody (mAb) 44G4 but more mAbs against endoglin have been discovered, giving more ways to identify it in tissues.It is suggested that endoglin has 5 potential N-linked glycosylation sites in the N-terminal domain and an O-glycan domain near the membrane domain that is rich in Serine and Threonine.