The recipients of the 2025 Nobel Prize in Physiology or Medicine are Mary E. Brunkow, Fred Ramsdell and Shimon Sakaguchi. They won the prize for their discoveries concerning peripheral immune tolerance. Photo by Claudio Bresciani/EPA
Three scientists were awarded the Nobel Prize in Physiology or Medicine Monday for their work to explain how the body protects itself from autoimmune diseases.
The Nobel Assembly at Karolinska Institutet announced Monday that Mary E. Brunkow, Fred Ramsdell of the United States and Shimon Sakaguchi of Japan won the prize, worth $1.17 million, which will be divided among the three of them.
The laureates identified the immune system’s security guards, regulatory T cells, which prevent immune cells from attacking our own bodies, the Nobel Prize’s press release said.
“Their discoveries have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases,” said Olle Kämpe, chair of the Nobel Committee, in a statement.
Autoimmune diseases like rheumatoid arthritis, lupus, Type 1 diabetes and many more happen when our immune system attacks parts of our own bodies. Some can be fatal.
“T regulatory cells play an absolutely vital role in preventing or ameliorating their impact,” Daniel Kastner, distinguished investigator at the National Institutes of Health, told CNN.
Sakaguchi found in 1995 that the immune system is more complex than previously thought and discovered a previously unknown class of immune cells that protect the body from autoimmune diseases.
Brunkow and Ramsdell discovered in 2001 why a specific mouse strain was particularly vulnerable to autoimmune diseases. They learned 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, which usually shows up in infancy and requires a bone marrow transplant.
Two years later, Sakaguchi was able to link the discoveries. He proved that the Foxp3 gene governs the development of the cells he identified in 1995. These regulatory T cells monitor other immune cells and ensure that our immune systems tolerate our own tissues.
These discoveries launched the field of peripheral tolerance, spurring the development of medical treatments for cancer and autoimmune diseases. Several treatments are now in clinical trials.
The laureates are:
— Brunkow, 64, has a Ph.D from Princeton University and is senior program manager at the Institute for Systems Biology, Seattle.
— Ramsdell, 65, got his Ph.D from the University of California Los Angeles and is scientific advisor at Sonoma Biotherapeutics in San Francisco.
— Sakaguchi, 74, got his Ph.D from Kyoto University, Japan. He is a distinguished professor at the Immunology Frontier Research Center at Osaka University.
The rest of the Nobel prizes will be announced this week.
