Proessor Shimon Sakaguchi at a press conference held at the University of Osaka after the annoucement of his Nobel Prize on Oct. 6.
STOCKHOLM — The Nobel Assembly at Karolinska Institutet has decided to award the 2025 Nobel Prize in Physiology or Medicine to Mary E. Brunkow, Institute for Systems Biology, Seattle; Fred Ramsdell, Sonoma Biotherapeutics, San Francisco; and Shimon Sakaguchi, Osaka University,.
They discovered how the immune system is kept in check.
The body’s powerful immune system must be regulated, or it may attack our own organs. Brunkow, Ramsdell and Sakaguchi are being recognized for their groundbreaking discoveries concerning peripheral immune tolerance that prevents the immune system from harming the body.
Every day, our immune system protects us from thousands of different microbes trying to invade our bodies. These all have different appearances, and many have developed similarities with human cells as a form of camouflage. So how does the immune system determine what it should attack and what it should defend?
Brunkow, Ramsdell and Sakaguchi identified the immune system’s security guards, regulatory T cells, which prevent immune cells from attacking our own body.
“Their discoveries have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases,” says Olle Kämpe, chair of the Nobel Committee.
“I believe this will encourage immunologists and physicians to apply the T regulatory cells to treat various immunological diseases,” Sakaguchi said in an interview with the Nobel Prize’s Adam Smith.
Sakaguchi was swimming against the tide in 1995, when he made the first key discovery. At the time, many researchers were convinced that immune tolerance only developed due to potentially harmful immune cells being eliminated in the thymus, through a process called central tolerance.
Sakaguchi showed that the immune system is more complex and discovered a previously unknown class of immune cells, which protect the body from autoimmune diseases.
Brunkow and Ramsdell made the other key discovery in 2001, when they presented the explanation for why a specific mouse strain was particularly vulnerable to autoimmune diseases. They had discovered that the mice have a mutation in a gene that they named Foxp3. They also showed that mutations in the human equivalent of this gene cause a serious autoimmune disease, IPEX.
Two years after this, Sakaguchi was able to link these discoveries. He proved that the Foxp3 gene governs the development of the cells he identified in 1995. These cells, now known as regulatory T cells, monitor other immune cells and ensure that our immune system tolerates our own tissues.
The laureates’ discoveries launched the field of peripheral tolerance, spurring the development of medical treatments for cancer and autoimmune diseases. This may also lead to more successful transplantations. Several of these treatments are now undergoing clinical trials.
The prize of 11 million kronor ($1.2 million) will be shared equally among the three recipients.
Born in Shiga Prefecture, Sakaguchi earned his medical degree from Kyoto University in 1976, left its graduate program in 1977 to join the Aichi Cancer Center for more in-depth research, and returned to Kyoto University to earn a Ph.D. in 1983. In 2015, he received the Gairdner International Award for his contributions to medical science.