Three Scientists Win the 2025 Nobel Prize in Medicine for Discovering the Immune System's Guard Cells
On October 6, 2025, in Stockholm, Sweden, the Nobel Assembly at Karolinska Institutet announced that the 2025 Nobel Prize in Physiology or Medicine was awarded to Mary E. Brunkow, Fred Ramsdell and Shimon Sakaguchi, for their discoveries concerning peripheral immune tolerance.
The three identified the immune system's security guards, regulatory T cells, which monitor other immune cells and prevent the immune system from attacking the body's own tissues. Olle Kämpe, chair of the Nobel Committee, said their discoveries have been decisive for understanding how the immune system functions and why we do not all develop serious autoimmune diseases.
Sakaguchi made the first key discovery in 1995. At the time, many researchers were convinced that immune tolerance developed only because potentially harmful immune cells were eliminated in the thymus, a process called central tolerance. Sakaguchi showed the immune system is more complex and discovered a previously unknown class of immune cells that protect the body from autoimmune diseases, cells now known as regulatory T cells.
Brunkow and Ramsdell made the other key discovery in 2001. Working with a mouse strain that was particularly vulnerable to autoimmune diseases, they found the mice had a mutation in a gene they named Foxp3, and showed that mutations in the human equivalent of the gene cause a serious autoimmune disease, IPEX. Two years later, Sakaguchi linked the two lines of work, proving that the Foxp3 gene governs the development of regulatory T cells.
The Nobel Assembly said the laureates' discoveries launched the field of peripheral tolerance, spurring the development of medical treatments for cancer and autoimmune diseases and potentially more successful transplantations, with several treatments now in clinical trials. Brunkow is at the Institute for Systems Biology in Seattle, Washington, Ramsdell is a scientific adviser at Sonoma Biotherapeutics in San Francisco, California, and Sakaguchi is a distinguished professor at Osaka University in Japan. The three will share the prize of 11 million Swedish kronor equally.
Related: Venezuelan Opposition Leader Machado Wins the 2025 Nobel Peace Prize
(Source: The Nobel Assembly at Karolinska Institutet)
Source: The Nobel Assembly at Karolinska Institutet
Published by GSM · USA (original Chinese edition)
Photo: 图：坂口志文资料照片。CC BY 4.0，经 Wikimedia Commons。 / Photo: Shimon Sakaguchi in a file photo. CC BY 4.0, via Wikimedia Commons.
- 2025-10-06Three Scientists Win the 2025 Nobel Prize in Medicine for Discovering the Immune System's Guard CellsThis story
- 2025-10-08Three Scientists Win the 2025 Nobel Prize in Chemistry for Developing Metal-Organic Frameworks
