Nobel Prize 2025 winners: Who are Mary Brunkow, Fred Ramsdell and Shimon Sakaguchi?
The 2025 Medicine Nobel honors immune “security guard” discoveries that could lead to new treatments for cancer and autoimmune diseases.
Scientists Mary Brunkow, Fred Ramsdell, and Shimon Sakaguchi were awarded the Nobel Prize in Physiology or Medicine 2025. The trio was recognized for their pioneering discoveries on peripheral immune tolerance: the process that allows the immune system to fight harmful microbes without turning against the body’s own cells, reported Reuters.
The Nobel Assembly at Sweden’s Karolinska Institute described their work as “decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases.” The laureates will share a prize of 11 million Swedish crowns (nearly $1.2 million) with gold medals presented by Sweden’s King Carl XVI Gustaf.
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Regulatory T cells
The three scientists’ research centers on regulatory T cells (Tregs), which act as the immune system’s security guards. These cells ensure that immune defenses do not mistakenly attack healthy tissue. Their discoveries have opened new avenues for treating conditions like multiple sclerosis, inflammatory bowel disease, and type 1 diabetes, while also showing promise for cancer treatments.
Currently, more than 200 clinical trials involving Tregs are underway worldwide, according to the Karolinska Institute.
Shimon Sakaguchi: Swimming against the tide
According to the Nobel Prize’s press statement, Shimon Sakaguchi, 74, first identified a new class of T cells in 1995, challenging the prevailing belief that immune tolerance was only established in the thymus. His work proved that the immune system was more complex and that Tregs were key to preventing autoimmune diseases.
At a press conference in Osaka, Sakaguchi, who is a professor at Osaka University, said he did not expect such recognition so soon, Reuters reported. He was quoted in the report saying, “I used to think some reward may be forthcoming if what we were doing will advance a little further and it will become more beneficial to people in clinical settings.”
During the event, Japan’s Prime Minister Shigeru Ishiba called to congratulate him. When asked about cancer treatment, Sakaguchi stated he believed a time would come when cancer would be “no longer a scary disease, but a curable one.”
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Mary Brunkow and Fred Ramsdell: The Foxp3 breakthrough
In 2001, Mary Brunkow and Fred Ramsdell made an important advancement while investigating the scurfy mouse strain developed by another researcher who was studying autoimmune disease in mice. They identified that scurfy depended upon a defect in a gene they called Foxp3, the Nobel Prize organization press statement added.
Later, they demonstrated that when Foxp3 is mutated in humans, this results in a catastrophic autoimmune disease called IPEX syndrome. In 2003, Sakaguchi was able to merge these findings with his own discoveries from 1995 to demonstrate that Foxp3 is required to develop regulatory T cells.
Brunkow, who was born in 1961, serves as a senior program manager at the Institute for Systems Biology in Seattle, where he is engaged with genomics and molecular biology, according to Reuters.
The outlet added that Ramsdell, 64, is a long-time immunologist and is acting as a scientific adviser at Sonoma Biotherapeutics in San Francisco. He had carried out important research in immune cells prior to moving to the National Institutes of Health and was responsible for advances in T cells and T cell tolerance.
FAQs
Q: Who won the 2025 Nobel Prize in Physiology or Medicine?
A: Mary Brunkow, Fred Ramsdell, and Shimon Sakaguchi.
Q: What was their discovery?
A: They identified regulatory T cells, which prevent the immune system from attacking the body’s own tissues.
Q: Why is this discovery important?
A: It explains how the immune system avoids autoimmune diseases and opens possibilities for new cancer and autoimmune treatments.
