Anti-Fibrinogen single-domain antibody.

Fibrinogen (coagulation factor I) is a glycoprotein complex that circulates in the blood of vertebrates. It consists as a dimer of 3 pairs of non-identical chains, Aα, Bβ and γ, which are cross-linked by disulfide bonds in their N-terminal segments. Additionally, the molecule has 2 terminal D domains and one central E domain. During injury fibrinogen is converted enzymatically by thrombin to form individual fibrin strands by attacking the N-terminus of the Aα and chains. The individual fibrin strands polymerize and are crosslinked by blood coagulation factor XIIIa to form an extensive interconnected fibrin network, which forms the basis for the formation of a mature fibrin clot. In addition, fibrinogen connects platelets through binding to fibrinogen receptor integrin αIIbβ3 (GPIIbIIIa), mediates platelet and endothelial cell spreading, fibroblast proliferation, capillary tube formation, and angiogenesis and thereby promote revascularization and wound healing. Elevated levels of fibrinogen can cause thrombosis and associated vascular injury.