News
Mary Brunkow and Fred Ramsdell of the United States, together with Japan’s Shimon Sakaguchi, have been jointly awarded the 2025 Nobel Prize in Physiology or Medicine.
Their work revealed the mechanism by which the immune system prevents itself from attacking the body’s own cells — a process known as peripheral immune tolerance.
According to the Nobel Assembly at Sweden’s Karolinska Institute, the three scientists were recognized “for their discoveries revealing how the immune system restrains excessive reactions while still maintaining its ability to fight infection.”
At a press conference in Osaka, Sakaguchi expressed surprise at the award and said, “It would be rewarding if this recognition leads to further development and clinical applications.”
During the event, he even received a congratulatory phone call directly from the Japanese Prime Minister.
The prize includes a monetary award of 11 million Swedish kronor (approximately USD 1.2 million) and the traditional Nobel gold medal.
The awarded research identified that regulatory T cells (Tregs) — a subset of white blood cells — act as a “brake” on the immune response.
This discovery laid the foundation for new approaches to autoimmune diseases and cancer immunotherapy.
Source: Reuters
What is the Nobel Prize in Physiology or Medicine?
The Nobel Prizes were established in accordance with the 1895 will of Swedish chemist Alfred Nobel, and were first awarded in 1901 to individuals who have made “the greatest benefit to humankind.”
The six categories are Physics, Chemistry, Physiology or Medicine, Literature, Peace, and Economic Sciences, and the laureates are announced every October.
The Physiology or Medicine Prize honors researchers who have deepened our understanding of life and health and contributed to the progress of medicine.
Past laureates include the discovery of penicillin (1945), the structure of DNA (1962), and the development of immune checkpoint therapy (2018, Tasuku Honjo).
Peripheral Immune Tolerance and the Discovery of Regulatory T Cells
This year’s Nobel Prize theme, “peripheral immune tolerance,” refers to the mechanism that prevents the immune system from attacking the body itself.
While immune cells are designed to eliminate viruses and bacteria, they can sometimes go rogue — attacking the body’s own tissues and organs. This malfunction is what causes autoimmune diseases.
Sakaguchi and his colleagues were the first to identify regulatory T cells (Tregs), which act as a brake on immune overreactions.
They elucidated both their function and molecular basis, showing how Tregs maintain immune balance.
This discovery revolutionized our understanding of autoimmune disorders such as rheumatoid arthritis and type 1 diabetes.
At the same time, this “immune brake” has deep implications for cancer therapy.
While Tregs prevent the immune system from turning against the body, they can also suppress immune attacks on tumor cells — allowing cancer to evade immune surveillance.
Modern immunotherapies such as checkpoint inhibitors aim to temporarily release this brake, reactivating immune cells to fight cancer.
Thanks to decades of research, immunology has entered a new era — one that focuses not only on “attacking enemies” but also on “knowing when to restrain.”
Sakaguchi’s discovery laid the very foundation for this paradigm shift.
Overseas Reactions
Below are selected comments from online discussions following the Nobel announcement:
The official PDF from the Nobel Foundation is great for anyone new to immunology. It explains the science very clearly.
https://www.nobelprize.org/uploads/2025/10/advanced-medicineprize2025.pdf
Thanks for sharing. I’m not an immunologist, but I work in a related field — can’t wait to read this with a cup of coffee.
I’m going to start calling autoimmune diseases “horror autotoxicus” — the horror of self-destruction. That term fits perfectly. Brilliant choice for the prize.
It feels like just yesterday that Tregs were “the new kid on the block” in immunology. Time flies.
Once again, the term “Physiology or Medicine Prize” feels outdated. The committee keeps honoring basic research while ignoring real clinical breakthroughs — TAVI, CFTR therapies, thrombectomy for stroke — none of them have received a Nobel yet. That says a lot about where the focus lies.
I’m not a scientist, but as a heart transplant recipient, I find immune tolerance fascinating.
Could this research — or others like it — one day help the body “accept” a transplanted organ as its own?
If so, maybe we could stop taking immunosuppressants someday.
If we could train the immune system to accept new organs, it would be revolutionary — no more beating the immune system into submission with drugs.
Absolutely. We’re not there yet, but thanks to people in this field, we’re getting closer.
To truly eliminate rejection, we’d probably need to tailor regulatory T cells to match the genetic profile of the transplanted organ — creating patient-specific Tregs that bridge the two systems.
I haven’t heard much lately, but Duke University had a team experimenting with thymus–heart co-transplants in infants, aiming to eliminate lifelong immunosuppressants.
What exactly did they discover to earn the Nobel? I remember learning about FoxP3 and Tregs years ago.
What year was that?
Remember, Nobels often come decades after the discovery.
I think our professors were teaching cutting-edge findings even before they were officially recognized.
Around 2017 or 2018, I think. It’s funny — I thought it was already established science back then. Turns out it was still pretty recent. Guess we were learning history in real time.
Analysis and Commentary
The 2025 Nobel Prize in Physiology or Medicine is more than a personal accolade — it serves as a mirror reflecting the direction of modern science.
This year’s theme, “peripheral immune tolerance,” celebrates fundamental biological insight rather than a specific treatment or device — a trend increasingly evident over the past decade.
A Return to Fundamentals
In recent years, the Nobel Assembly has leaned toward honoring basic biological discoveries rather than immediate clinical breakthroughs.
From Yoshinori Ohsumi’s autophagy (2016) to Piezo ion channels (2021) and ancient DNA analysis (2022), these awards have all emphasized understanding life’s fundamental mechanisms over direct medical application.
Sakaguchi’s work fits this pattern.
Immunology intersects deeply with real-world medicine — cancer, infection, autoimmune disease — yet what was recognized here is the core principle that keeps the immune system from turning against itself.
The Nobel Committee seems to reaffirm that transforming human knowledge outweighs immediate therapeutic value.
Japan’s Role and Global Collaboration
This award also symbolizes a revival of Japan’s influence in fundamental biomedical science.
Although Japanese research is sometimes criticized for its limited focus on applied innovation, Sakaguchi’s decades-long pursuit of immune tolerance has achieved global recognition.
Importantly, this was a Japan–U.S. collaboration, highlighting how cross-border research continues to shape modern life sciences.
The broader impact of this discovery extends into politics and economics as well.
Understanding immune tolerance underpins advances in cancer therapy, organ transplantation, and autoimmune drug development, with huge implications for the global pharmaceutical market.
In Japan, research hubs like Kyoto University and RIKEN, along with biotech startups, are already exploring Treg-based therapies — and this Nobel Prize could spur new funding and investment.
What This Prize Says About Science
Critics online have once again pointed out that “basic research” dominates, while transformative clinical innovations — like TAVI, CFTR therapies, and stroke thrombectomy — remain unrecognized.
However, the Nobel ethos has always valued discovery over invention — knowledge that permanently reshapes how humanity understands life.
In that light, Sakaguchi’s work exemplifies the prize’s deepest intent.
Modern science continues to balance two philosophies: research that helps now versus research that changes everything later.
This year’s Nobel firmly tilts toward the latter — and Japan’s role in that story underscores the enduring power of long-term, curiosity-driven inquiry.
Conclusion
The 2025 Nobel Prize in Physiology or Medicine highlights one of the most profound questions in biology:
“Why doesn’t the human body attack itself?”
Sakaguchi’s discovery of regulatory T cells revealed that the immune system’s strength lies not only in aggression but also in restraint.
It’s a reminder that science isn’t just about curing disease — it’s about understanding what it means to be alive.
While some online debates lamented the lack of clinical focus, this Nobel honors a different kind of progress — one measured not in years, but in centuries.
A hundred years from now, medicine will stand on the quiet foundations laid by discoveries like this.
Science’s true essence lives not in the results we see, but in the relentless act of asking “why” and “how.”
And this year’s Nobel Prize is proof that spirit endures.
References
Reuters: Immune system breakthrough wins Nobel medicine prize for US, Japan scientists
Reddit: The Nobel Prize in Physiology or Medicine 2025 – Brunkow, Ramsdell & Sakaguchi
Reddit: Nobel Prize 2025 for regulatory T-cells and Immunological tolerance
