Significance of plasma fibronectin.

Fibronectin and fibrinogen are unique proteins, since they both are present in a soluble form in plasma and in an insoluble form in connective tissue. The insoluble fibronectin is always present in connective tissue, while the presence of fibrin is temporary. The two proteins may be associated under various conditions. Fibronectin is incorporated into polymerizing fibrin, e.g. in the tissue repair process and during thrombus formation. Fibronectin is also associated with other biological structures, such as collagen of all types, sulphated proteoglycans, blood platelets and the cell walls of Staphylococcus aureus. These properties result in a depletion of plasma fibronectin in certain clinical situations, such as disseminated intravascular coagulation (DIC), traumatic shock and severe burns. The decreased plasma fibronectin concentration might result in an increased fibrin polymer concentration in the circulation, thus accentuating the microvascular thromboses and the coagulation factor consumption in DIC. The practical clinical implication is that a low plasma concentration of fibronectin might define a group of patients with a high risk of developing DIC.