TNFSF18 (TNF Superfamily Member 18): TNFSF18 is a molecule that reflects the regulation of immune responses in the body. Also known as GITR ligand, it binds to GITR on T cells and regulatory T cells, promoting effector T cell activity while suppressing regulatory T cell function. This dual role makes TNFSF18 a key target in cancer immunotherapy and autoimmune disease treatment.