TL-1A belongs to the TNF superfamily of ligands. It is expressed predominantly in endothelial cells, and to a lesser extent in the placenta, lung, kidney, skeletal muscle, pancreas, small intestine and colon. TL-1A inhibits endothelial cell proliferation and angiogenesis, and has been shown to induce NF-kappaB activation, caspase activity, and apoptosis in responding cell lines. TL-1A interacts with TNFRSF25/DR3 receptor, but can also bind to a decoy receptor TNFRSF21/DR6. Recombinant Human TL-1A is a 22.0 kDa polypeptide of 194 amino acid residues.