Gunilla Karlsson Hedestam (left) and Olle Kampe (center), members of the Nobel Assembly at the Karolinska Institutet, along with Marie Wahren-Herlenius (right), Professor of Rheumatology at the Karolinska Institutet, are seen seated in front of a large screen showing the portraits of Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi during a press conference announcing the winners of the 2025 Nobel Prize in Physiology or Medicine at the Karolinska Institute in Stockholm, Sweden, on October 6, 2025.
This year’s award was jointly given to Mary Brunkow and Fred Ramsdell of the United States and Shimon Sakaguchi of Japan for their groundbreaking discoveries in the field of “peripheral immune tolerance,” a key mechanism by which the immune system prevents the body from attacking its own healthy tissues. Their research has played an essential role in understanding autoimmune diseases and has helped shape new therapeutic approaches for conditions such as multiple sclerosis, type 1 diabetes, rheumatoid arthritis, and inflammatory bowel disease.
Shimon Sakaguchi, a leading Japanese immunologist, was among the first to identify regulatory T cells (Tregs), a specialized group of immune cells responsible for suppressing excessive immune responses and maintaining tolerance to self-antigens. His pioneering work dating back to the 1990s reshaped scientific understanding of immune regulation and laid the groundwork for a new era of immunological research.
Mary Brunkow and Fred Ramsdell further advanced the field through their collaborative discovery of the FOXP3 gene, which is crucial for the development and function of regulatory T cells. Their research clarified the genetic basis of immune tolerance and explained the mechanisms underlying fatal autoimmune disorders such as IPEX syndrome (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked syndrome). By uncovering how mutations in FOXP3 disrupt immune balance, their findings opened pathways for targeted treatment strategies.
During the press conference, members of the Nobel Committee highlighted the global impact of these discoveries, noting that therapies inspired by their work are currently being explored in clinical trials aimed at restoring immune tolerance or modulating overactive immune responses. The committee emphasized that their combined contributions have transformed both basic immunology and translational medicine, offering new hope for patients with chronic autoimmune and inflammatory diseases.
The announcement drew international attention from the scientific community, with experts praising the laureates for decades of research that bridged laboratory science and medical application. The Nobel Prize in Physiology or Medicine is traditionally the first prize announced each Nobel season and sets the tone for the subsequent awards in physics, chemistry, literature, peace, and economics.
The official Nobel Prize award ceremony is scheduled to take place in Stockholm in December, where the laureates will receive their medals, diplomas, and a share of the prize money in the presence of the Swedish royal family. Their achievements are expected to inspire further research into immune system regulation and precision medicine in the years ahead.
