Tumor necrosis factor receptor superfamily member 18(Gitr) contains 3 TNFR-Cys repeats and it have four isforms.IsformA、isformB and isformC is single-pass type I membrane protein and isformD is a secreted protein. The protein is the receptor for TNFSF18.It seems to be involved in interactions between activated T-lymphocytes and endothelial cells and in the regulation of T-cell receptor-mediated cell death. It mediated NF-kappa-B activation via the TRAF2/NIK pathway.It binds to TRAF1, TRAF2, and TRAF3, but not TRAF5 and TRAF6 and binds through its C-terminus to SIVA1/SIVA.It preferentially expressed in activated T lymphocytes and up-regulated in peripherical mononuclear cells after antigen stimulation/lymphocyte activation.