Americans Win 2025 Nobel Prize in Medicine

Key Points

• Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi share this year’s Nobel Prize in Medicine.
• Their research revealed how the immune system regulates itself to avoid attacking healthy cells.
• The findings opened new paths for therapies targeting autoimmune and cancer-related conditions.
• The winners will divide prize money worth nearly $1.2 million.

Three scientists from the U.S. and Japan have earned the 2025 Nobel Prize in Medicine for their pioneering research into the body’s immune tolerance system. Their work uncovered how specific immune cells stop the body from attacking its own tissues — a process essential for preventing autoimmune disease.

Japanese immunologist Shimon Sakaguchi first identified a unique group of immune cells in the mid-1990s that help keep the immune system in balance. Years later, American researchers Mary E. Brunkow and Fred Ramsdell pinpointed the gene, known as Foxp3, that allows these cells — now called regulatory T cells — to function properly. Together, their discoveries reshaped how scientists understand immune control and paved the way for new approaches to treating diseases such as multiple sclerosis, rheumatoid arthritis, and even certain cancers.

Experts say the trio’s work has already led to major advances in medicine, influencing therapies that help the immune system fight illness without damaging healthy tissues. It’s also expected to make organ transplants safer and more successful.

The Nobel Committee praised the discovery for fundamentally changing how doctors approach immune-related disorders. The laureates will officially receive their awards in Stockholm on December 10, marking another milestone in the history of modern immunology.