Nobel Prize in Medicine Goes to 3 Scientists for Immune System Discovery/ Newslooks/ WASHINGTON/ J. Mansour/ Morning Edition/ The 2025 Nobel Prize in Physiology or Medicine was awarded to Mary E. Brunkow, Fred Ramsdell, and Dr. Shimon Sakaguchi for uncovering key mechanisms behind immune system regulation. Their discoveries around regulatory T cells and the Foxp3 gene revealed how the body prevents autoimmune diseases. The trio’s research laid the foundation for potential future therapies in immunology and cancer.
Nobel Prize Immune System Research Quick Looks
- Nobel Prize in Medicine 2025 awarded to three scientists for immune system discoveries.
- Mary E. Brunkow, Fred Ramsdell, and Dr. Shimon Sakaguchi recognized for research on peripheral immune tolerance.
- Discovery of regulatory T cells (T-regs) and the Foxp3 gene changed understanding of autoimmune disease prevention.
- Sakaguchi first identified T-reg cells in 1995; Brunkow and Ramsdell linked Foxp3 to immune system failures in 2001.
- The trio shares nearly $1.2 million in prize money (11 million Swedish kronor).
- Their work opened a new field in immunology with implications for autoimmune diseases and cancer.
- Scientists hope findings will translate into future clinical therapies.
- The Nobel was announced by the Karolinska Institute; the ceremony is set for December 10.
- Prime Minister of Japan called Sakaguchi to congratulate him on his global contribution.
- Brunkow learned of the win through an AP photographer after missing the initial call.
Deep Look
2025 Nobel Prize in Medicine Awarded to Scientists for Pioneering Research on Immune System Regulation
STOCKHOLM — The 2025 Nobel Prize in Physiology or Medicine has been awarded to Mary E. Brunkow, Fred Ramsdell, and Dr. Shimon Sakaguchi for their pivotal work in unraveling how the human immune system avoids attacking itself — a discovery that fundamentally reshaped our understanding of autoimmune diseases.
The Nobel Committee at Sweden’s Karolinska Institute announced Monday that the trio’s findings around peripheral immune tolerance have laid the groundwork for future treatments in both autoimmune conditions and cancer.
“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.
The laureates will share a prize of 11 million Swedish kronor, equivalent to nearly $1.2 million USD. The award ceremony is scheduled for December 10, commemorating the anniversary of Alfred Nobel’s death.
What Their Research Uncovered
The human immune system is built to recognize and destroy foreign invaders like viruses and bacteria. T cells, a type of immune cell, are trained to distinguish between harmful outsiders and the body’s own cells. If this recognition process goes awry, it can lead to autoimmune diseases — where the immune system mistakenly attacks healthy tissues.
Previously, scientists believed central tolerance — the process of eliminating faulty T cells in the thymus — was the key mechanism preventing this. However, the 2025 Nobel laureates identified a secondary defense system, known as peripheral tolerance.
- In 1995, Dr. Shimon Sakaguchi discovered a new type of immune cell called regulatory T cells (T-regs) that act as immune system moderators.
- In 2001, working at a biotech company, Mary E. Brunkow and Fred Ramsdell discovered a mutation in the Foxp3 gene, which caused immune overreactions in mice.
- Later, Sakaguchi connected the dots, revealing that Foxp3 is essential for the development of T-regs.
These cells essentially act as internal “security guards,” suppressing overactive immune responses that could otherwise harm the body.
Brunkow told the Associated Press that their team had to use cutting-edge technology to isolate the genetic mutation responsible for immune malfunction in mice.
“It was a really small alteration in DNA that caused a massive change to how the immune system works,” she said.
Why It Matters
The trio’s work opened a new branch of immunology, according to Karolinska Institute rheumatology professor Marie Wahren-Herlenius. Researchers now explore ways to leverage regulatory T cells to develop new therapies — particularly for autoimmune disorders and cancer.
Dr. Jonathan Schneck, an immunology professor at Johns Hopkins, praised the significance of the discovery, noting that the immune system’s internal checks were far more complex than previously understood.
Although treatments based directly on their work are not yet in widespread use, Schneck said the foundation has been laid for breakthrough therapies in the coming years.
“We’re reaping the benefits of this research, but there’s still so much more to come,” he added.
Reactions from the Laureates
Thomas Perlmann, secretary-general of the Nobel Committee, said he was only able to reach Dr. Sakaguchi before the announcement.
“He was incredibly grateful, honored, and quite moved by the news.”
At a press conference later, Sakaguchi described the prize as “a happy surprise” and emphasized the importance of collaboration, noting that his research was once seen as fringe.
“In the beginning, it was not a popular field. But with the help of fellow researchers, we made progress,” he said.
During the event, he received a personal call from Japan’s Prime Minister Shigeru Ishiba, who asked about the future clinical applications of his research. Sakaguchi responded cautiously:
“Hopefully we can reach that stage in about 20 years… But science will advance, and cancer may soon be treatable.”
Meanwhile, Mary Brunkow found out about her Nobel win from an Associated Press photographer who arrived at her home in Seattle after she ignored a call from Sweden.
“I saw the number and thought it was spam,” she laughed.
Her husband, Ross Colquhoun, added:
“When I told Mary she won, she said, ‘Don’t be ridiculous.’”
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