Mary Brunkow, Fred Ramsdell, and Shimon Sakaguchi were awarded the 2025 Nobel Prize in Physiology or Medicine for their discoveries on how the body controls harmful T-cells, advancing understanding of autoimmune diseases. The Karolinska Institutet in Stockholm said the trio’s work revealed the mechanism of “peripheral immune tolerance,” which prevents the immune system from attacking the body’s own tissues. The discovery has paved the way for new treatments for autoimmune diseases and cancer. Brunkow and Ramsdell are based in the US, while Sakaguchi continues his research in Japan. The winners will receive a gold medal and 11 million Swedish kronor (about $1.2 million) at the award ceremony in December.