Human Vitronectin/VTN is a cell adhesion and spreading factor. It can be found in the blood and the extracellular matrix (ECM). Vitronectin interacts with glycosaminoglycans and proteoglycans. The multimeric Vitronectin can efficiently bind to and incorporate into the ECM; Vitronectin can support cell adhesion through binding to various integrins and other proteoglycans. Vitronectin can be recognized by certain members of the integrin family and serves as a cell-to-substrate adhesion molecular. It can as a inhibitor of the membrane-damaging effect of the terminal cytolytic complement pathway. Vitronectin contains an endogenous cleavage site, plus cleavage sites for elastase, thrombin, and plasmin.