On October 6th, 2025, the Nobel Assembly awarded the 2025 Nobel Prize in Physiology or Medicine to Mary E. Brunkow, Fred Ransdell, and Shimon Sakaguchi for their groundbreaking work relating to the immune system. Specifically, the “groundbreaking work” was related to peripheral immune tolerance—a fundamental mechanism that stops the immune system from attacking its own bodily tissue. This mechanism is vital for preventing autoimmune diseases and maintaining immune system balance. Without this critical process, the immune system would not be able to distinguish between harmful invaders and the body’s own cells.
Their Role and Discoveries
In 1995, Sakaguchi discovered the existence of regulatory T cells, which he claimed prevented autoimmune attacks. Later, in 2001, Brunkow and Ramsdell found that IPEX, an autoimmune disease, was caused by mutations in the FOXP3 gene. With this base information, Sakaguchi later found that the creation of regulatory T cells depended on the FOXP3 gene. This established a direct genetic and functional link between regulatory T cells and immune tolerance. Not only explaining how the immune system regulates itself, but also explaining what happens when this regulation breaks down.
Why It Matters
Their discoveries have now reshaped scientists’ understanding of autoimmune diseases, immunodeficiency, and even cancer on a molecular and cellular level, which sophomore Zoya Ahmed describes as “a big [deal].” Their discoveries also helped explain how the immune system maintains balance. These insights have influenced not only basic research, but also clinical approaches to treating immune-related conditions. In particular, their findings have paved the way for new immunotherapies, which seek to either intensify or diminish the immune response depending on the condition being treated.
Furthermore, this brand-new understanding of autoimmune diseases, cancer, and other complex medical conditions allows for more advancements in the development of more targeted and effective treatments. This knowledge can now help with the development of new treatments, which many, such as Zoya Ahmed, claim will be “helpful to a lot of people now and in the future.”
A Lasting Impact
As the world continues to grow and grapple with the complexity of the immune system, this year’s Nobel Prize in Physiology or Medicine serves as a powerful reminder of the value of science and medical research. And by deepening our knowledge on how the immune system works, scientists have not only laid out a new foundation for a new era in medicine, but have also opened new doors to treating some of the most challenging diseases of the 21th century.
