TNFSF18 (TNF Superfamily Member 18): TNFSF18 is a molecule involved in regulating immune responses in the body. Also known as the 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 role makes TNFSF18 a crucial target in cancer immunotherapy and autoimmune disease treatment.