Stockholm, October 6, 2025: The 2025 Nobel Prize in Physiology or Medicine has been awarded to Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi for their groundbreaking discoveries on peripheral immune tolerance — a key mechanism that prevents the immune system from attacking the body’s own tissues.
Announcing the winners, the Royal Swedish Academy of Sciences said the laureates’ findings were crucial in identifying regulatory T cells (Tregs) — the “security guards” of the immune system. These cells play a vital role in preventing autoimmune diseases such as Type 1 diabetes, lupus, and rheumatoid arthritis.
“Their discoveries have been decisive for understanding how the immune system functions and why most people do not develop severe autoimmune disorders,” said Olle Kämpe, Chair of the Nobel Committee.
Pioneering Discoveries That Transformed Immunology
In 1995, when scientists believed immune tolerance was only controlled by a mechanism known as central tolerance, Shimon Sakaguchi made a revolutionary discovery — a new class of immune cells that prevent the body from attacking itself.
Years later, in 2011, Mary Brunkow and Fred Ramsdell identified that a specific strain of mice developed autoimmune diseases due to a mutation in a gene they named Foxp3. Their research further revealed that mutations in the human version of this gene lead to IPEX syndrome, a rare but severe autoimmune condition.
By 2013, Sakaguchi connected these findings and demonstrated that the Foxp3 gene regulates the development of regulatory T cells, which act as immune moderators to maintain the body’s tolerance toward its own tissues.
About the Laureates
- Mary E. Brunkow, a Princeton University PhD, currently serves as Senior Program Manager at the Institute for Systems Biology, Seattle.
- Fred Ramsdell is a Scientific Advisor at Sonoma Biotherapeutics, USA.
- Shimon Sakaguchi is a Distinguished Professor at the Immunology Frontier Research Center, Osaka University, Japan.
Legacy of the Nobel Prize in Medicine
Last year’s Medicine Nobel was awarded to Victor Ambros and Gary Ruvkun for their discovery of microRNA and its role in gene regulation.
The Nobel Prize, established by Swedish inventor Alfred Nobel, continues to honor individuals who “have conferred the greatest benefit to humankind.” The 2025 laureates will share a cash prize of 11 million Swedish kronor (approximately $1.2 million) during the award ceremony on December 10 in Stockholm.