The 2025 Nobel Prize in Medicine honors the discovery of how regulatory T cells prevent the immune system from attacking the body.
- Nobel Prize 2025 awarded for discoveries on immune regulation
- Tregs and Foxp3 gene prevent self-attacks by the immune system
- This finding opens new treatments for cancer and autoimmune diseases
Our immune system is like a powerful army, constantly defending us from bacteria, viruses, and other invaders. But what stops this army from mistakenly attacking our own organs? That mystery—how the immune system keeps itself in check—has earned Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi the 2025 Nobel Prize in Physiology or Medicine (1✔ ✔Trusted Source
They discovered how the immune system is kept in check
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Their discoveries revealed how a special set of “peacekeeping” immune cells, known as regulatory T cells (Tregs), prevent the body from turning against itself.
The Discovery of Immunity’s Hidden Brakes
All along researchers believed that thymus was the only organ in our body that could control immune tolerance until the mid-1990s. They thought that the organ was responsible for the destruction of deadly immune cells.
But in 1995, Shimon Sakaguchi disagreed with this assumption! He found that another set of T cells, marked by a protein known as CD25, acted as regulators, preventing immune cells from attacking the body tissues. These were referred to as regulatory T cells, or Tregs, which are regarded as the internal brakes of the immune system.
“Anyone who does not have an autoimmune disease, that’s because of these regulatory T cells,” says Markus Feuerer, an immunologist at the Leibniz Institute for Immunotherapy.
Foxp3 Gene—The Peacekeeper of Auto Immune Attacks
While Sakaguchi uncovered these mysterious cells, Mary Brunkow and Fred Ramsdell were researching a peculiar group of laboratory mice called scurfy mice that had severe autoimmune diseases. In 2001, they found that these mice possessed a faulty gene (Foxp3), located on the X chromosome.
They soon found that mutations in the human version of this gene caused a serious autoimmune disorder known as IPEX (X-linked disorder) that is common in boys. It was a breakthrough when Sakaguchi later proved that Foxp3 controlled the proliferation of Tregs—the very cells that prevent autoimmune attacks.
This discovery explained how the immune system is maintained and what happens when it fails.
We Have the Answer To How Immune System is Tuned
The work of these three scientists has revolutionized medicine. By understanding how Tregs operate, we have now enabled to tune the immune system, turning it up to combat cancer or calming it down to cure autoimmune diseases such as type 1 diabetes, lupus, or inflammatory bowel disease.
As of today, there are more than 200 clinical trials of Treg-based therapies. Some use interleukin-2, a natural compound that nourishes Tregs, while others test engineered Tregs to prevent organ rejection after transplants.
As Dr. Carola Vinuesa from the Francis Crick Institute says, “Their pioneering research uncovered one of the immune system’s most critical regulatory mechanisms.”
Field Researchers Are Applauding This Initiative
Field researchers applaud the Nobel committee’s choice to honor the three, who will divide the prize’s estimated $1.17 million monetary award. Holm Uhlig, a pediatrician at the University of Oxford who has worked with Ramsdell and specializes in inflammatory bowel disorders, calls the news “awesome”. It just demonstrates the progress the profession has made, from identifying this transcription factor to [creating] treatments and comprehending immunological tolerance. I’m so pleased; these are brilliant, brilliant people.”
Sakaguchi, who was speaking at a news conference hosted by the University of Osaka, said he was “surprised and honored” by the award. He also used the opportunity to thank the students and partners who helped make his study possible and to appreciate the larger efforts of the research field. He added, “I was never working alone—there were people all over the world who shared similar ideas,” he said. “I see this award as one that represents all of those people who have contributed to this research alongside me.”
Thanks to these groundbreaking discoveries, scientists now better understand how the immune system walks the fine line between defense and destruction. The 2025 Nobel laureates have not only explained how the body avoids attacking itself—but also opened the door to future cures for cancer, autoimmune diseases, and more successful organ transplants.
Reference:
- They discovered how the immune system is kept in check – (https://www.nobelprize.org/prizes/medicine/2025/press-release/)
Source-Medindia