Immune suppressive molecule that inhibits antigen-specific T-cell activation by acting as a major ligand of LAG3 (PubMed:30580966). Responsible for LAG3 T-cell inhibitory function (PubMed:30580966). Binds LAG3 independently from MHC class II (MHC-II) (PubMed:30580966). Secreted by, and promotes growth of, hepatocytes (By similarity). Homodimer (By similarity). Interacts (via the Fibrinogen C-terminal domain) with LAG3 (via Ig-like domains 1 and 2) (PubMed:30580966). Secreted in the blood plasma. Mainly expressed in liver (PubMed:12528893, PubMed:23483972). Also expressed in brown adipose tissue (PubMed:23483972). Mice develop normally but develop spontaneous autoimmune symptoms caused by T-cell activation in aged mice (PubMed:30580966). Mice also display slight metabolic defects: mice are heavier than wild type mates, have abnormal plasma lipid profiles, fasting hyperglycemia with enhanced gluconeogenesis and exhibit differences in white and brown adipose tissue morphology (PubMed:23483972). Blockade of the FGL1-LAG-3 interaction using a monoclonal antibody stimulates tumor immunity and is therapeutic against established mouse tumors in a receptor-ligand interdependent manner.