Brunkow, Ramsdell and Sakaguchi Share 2025 Nobel Prize for Immune System Research
Three scientists, Americans Mary Brunkow and Fred Ramsdell and Japan’s Shimon Sakaguchi, won the 2025 Nobel Prize in Physiology or Medicine for research that explains how the immune system avoids attacking the body’s own cells. Their work focuses on regulatory T cells, a type of white blood cell that acts like a brake for the immune system, preventing it from overreacting while still fighting infections.
The discoveries shed light on a process called peripheral immune tolerance, which controls how immune cells distinguish between threats and healthy tissue. Without this system, the body can attack itself, leading to autoimmune diseases. Brunkow and Ramsdell identified a gene called FOXP3, which marks these regulatory cells and is essential for their development. Sakaguchi’s work in Japan had previously suggested that these cells were key to maintaining immune balance. Brunkow said the cells are “rare but powerful” and serve as a braking system for the immune response. Sakaguchi, speaking at a press conference in Osaka, said he didn’t expect the award yet, noting that more clinical advances are still needed. During the press conference, he briefly took a call from Japan’s Prime Minister Shigeru Ishiba, who asked about the future of cancer therapy. Sakaguchi said he believes one day cancer could be curable.
Brunkow, Ramsdell, and Sakaguchi: Backgrounds
Ramsdell works as a scientific adviser at Sonoma Biotherapeutics in San Francisco, which develops therapies using regulatory T cells. Brunkow is senior program manager at the Institute for Systems Biology in Seattle, and Sakaguchi continues research and teaching at Osaka University. The three laureates will share a prize of 11 million Swedish crowns (about $1.2 million) and receive gold medals presented by Sweden’s king.
While their work is considered groundbreaking, no treatments based directly on regulatory T cells are available yet. There are more than 200 human trials in progress exploring how these cells could treat conditions like autoimmune diseases and chronic inflammation. Companies including Sonoma Biotherapeutics, Quell Therapeutics, and BlueRock are testing ways to control overactive immune responses in conditions such as inflammatory bowel disease. Jeffrey Bluestone, a longtime colleague of Ramsdell and co-founder of Sonoma, said Ramsdell’s work in identifying the FOXP3 gene in mice was a major breakthrough. “Those cells are the master regulators,” Bluestone said.
The Nobel Prize Tradition
The Nobel Prize in Medicine has been awarded since 1901 and is traditionally the first of the annual prizes. It recognizes contributions to science that expand understanding of human biology or have practical applications in medicine. Past winners include Alexander Fleming, who discovered penicillin, and more recently, researchers behind the mRNA COVID-19 vaccines.
This year’s award highlights basic science rather than a ready-made therapy. Understanding how the immune system restrains itself does not immediately translate into a new drug, but it provides a foundation for future work. Regulatory T cells could eventually be used to treat autoimmune conditions or improve immunotherapy for cancer, but those outcomes are still years away.
For Brunkow, Ramsdell, and Sakaguchi, the recognition is a culmination of decades of research. Brunkow found out about the prize at home in Seattle, woken up by her dog barking at a photographer on her porch. Sakaguchi expressed surprise and said he never expected the recognition to come before more clinical progress was made.
The Nobel Assembly praised the laureates for clarifying a part of the immune system that was poorly understood. Thomas Perlmann, Secretary of the Nobel Committee, stated that the discovery is a step towards potential therapies but not a cure yet.
What it Means for Future Research
The prize emphasizes the slow, methodical work of science. The discoveries do not immediately change patient care, but they create opportunities for treatments in the future. Whether regulatory T cells will become a tool for treating autoimmune diseases or cancer is still uncertain. For now, the award recognizes the understanding itself – how the immune system knows when to hold back and when to act. The Nobel Prize ceremonies take place on December 10, the anniversary of Alfred Nobel’s death, with a banquet in Stockholm. The medicine prize kicks off the week, followed by awards in physics, chemistry, literature, peace, and economics.
Brunkow, Ramsdell, and Sakaguchi’s work is part of a larger effort to understand and control the immune system. It’s technical, precise, and slow-moving, but it may eventually make treatments for autoimmune diseases and some cancers possible. For now, the focus is on understanding, not cures.
References
- Ahlander, J., Pollard, N., & Burger, L. (2025, October 6). Immune system breakthrough wins Nobel medicine prize for US, Japan scientists. Reuters.
- (2025, October 6). What are regulatory T-cells? Nobel-winning science explained. NDTV.
- (2025, October 6). ‘Don’t be ridiculous’: How medicine Nobel winners for 2025 reacted to the news. Hindustan Times.
- (n.d.). Nobel Prize award ceremonies. NobelPrize.org.
