Fibrinogenlike

Fibrinogen-like is a descriptive term used to refer to proteins that contain a domain molecularly related to fibrinogen, the liver-derived plasma glycoprotein essential for blood clot formation. In the human genome, the label is most often encountered in connection with fibrinogen-like protein 1 (FGL1) and fibrinogen-like protein 2 (FGL2). These proteins are not the same as the classical fibrinogen A, B and gamma chains, but they share a fibrinogen-like domain that underlies structural similarity.

FGL1, primarily produced by hepatocytes and secreted into blood, acts as a ligand for LAG-3, an immune checkpoint receptor on T cells. By engaging LAG-3, FGL1 can dampen T cell responses and modulate immune tolerance, with implications for cancer immunology and liver disease. It is being explored as a biomarker and therapeutic target in oncology and hepatitis.

FGL2 is produced by macrophages and dendritic cells and has a distinct role in coagulation. It possesses procoagulant activity and can generate fibrin via a prothrombinase-like mechanism, contributing to localized clot formation. FGL2 is implicated in transplant rejection, viral infections, and hepatic fibrosis, and is studied as a potential target to modulate coagulation and immune responses in such settings.

Across different species, fibrinogen-like proteins with similar domains have diverse functions in immunity, hemostasis, and tissue remodeling. The term fibrinogen-like is thus a structural descriptor rather than a single functional protein category.