Tumor necrosis factor ligand superfamily member 18 (TNFSF18) is also known as Glucocorticoid - induced TNF-related ligand (GITRL or GITR Ligand), Activation - inducible TNF - related ligand (AITRL), which belongs to the tumor necrosis factor family. TNFSF18 is expressed at high levels in the small intestine, ovary, testis, kidney and endothelial cells. TNFSF18 / GITRL is up-regulated after stimulation by bacterial lipopolysaccharides (LPS). TNFSF18 Can function as costimulator and lower the threshold for T-cell activation and T-cell proliferation. TNFSF18 / GITR Ligand is important for interactions between activated T-lymphocytes and endothelial cells. TNFSF18 also mediates activation of NF-kappa-B.