GITR, also known as TNFRSF18(CD357), belongs to the tumor necrosis factor receptor (TNF-R) superfamily. It is the receptor for TNFSF18. GITR plays a key role in dominant immunological self-tolerance maintained by CD25(+)CD4(+) regulatory T cells. GITR may be involved in interactions between activated T-lymphocytes and endothelial cells and in the regulation of T-cell receptor-mediated cell death. GITR and its ligand are important costimulatory molecules in the pathogenesis of autoimmune diseases. It also mediates NF-kappa-B activation via the TRAF2/NIK pathway.