Fibrinogen-like protein 1 (FGL1), a liver-secreted protein, is a major LAG-3 functional ligand independent from MHC-II. The FGL1-LAG-3 pathway maybe an important immune evasion mechanism and could contribute to current cancer immunotherapy efforts for several reasons. FGL1 inhibits antigen-specific T cell activation, and ablation of FGL1 in mice promotes T cell immunity. Blockade of the FGL1-LAG-3 interaction by monoclonal antibodies stimulates tumor immunity and is therapeutic against established mouse tumors in a receptor-ligand inter-dependent manner. FGL1 is highly produced by human cancer cells, and elevated FGL1 in the plasma of cancer patients is associated with a poor prognosis and resistance to anti-PD-1/B7-H1 therapy,FGL1,HFREP1,HP-041,LFIRE-1,LFIRE1,Cardiovascular,Blood,Coagulation,Serum Proteins,FGL1