TNFSF18 (TNF Superfamily Member 18): TNFSF18 is a molecule that plays a role in regulating immune responses within the body. Also referred to as GITR ligand, it binds to GITR on T cells and regulatory T cells, enhancing effector T cell activity while inhibiting regulatory T cell function. This dual function makes TNFSF18 an important target in cancer immunotherapy and the treatment of autoimmune diseases.