The Nobel Prize in Medicine 2025 was awarded in Stockholm to Mary E. Brunkow, Fred Ramsdell and Shimon Sakaguchi for discoveries on peripheral immune tolerance—the mechanisms that prevent the immune system from attacking the body’s own tissues.
The Nobel Assembly at Karolinska Institutet said the work has reshaped understanding of autoimmunity and opened paths for new therapies; the prize totals SEK 11 million (about €1.0 million), to be shared equally.
Why peripheral immune tolerance matters for disease
Peripheral immune tolerance complements central tolerance in the thymus by keeping reactive immune cells in check throughout life. Failures in this regulation can lead to autoimmune diseases such as type 1 diabetes, rheumatoid arthritis or lupus.
By identifying the cells and genes that enforce tolerance, the laureates’ research provided the conceptual basis for strategies that dampen pathological immunity without shutting down host defenses.
From Tregs to FOXP3: the discoveries behind the prize
In 1995, Sakaguchi identified a previously unknown class of T cells—regulatory T cells (Tregs)—that act as the immune system’s “security guards,” preventing immune cells from attacking self.
In 2001, Brunkow and Ramsdell linked devastating autoimmune disease in mice to mutations in FOXP3, and showed that mutations in the human equivalent cause IPEX syndrome. Subsequent work demonstrated that FOXP3 controls the development and function of Tregs, establishing a genetic and cellular framework for peripheral tolerance.
The laureates and their institutions
- Mary E. Brunkow, Senior Program Manager, Institute for Systems Biology (Seattle, USA).
- Fred Ramsdell, Scientific Advisor, Sonoma Biotherapeutics (San Francisco, USA).
- Shimon Sakaguchi, Distinguished Professor, Immunology Frontier Research Center, Osaka University (Japan).
How the Nobel Prizes are awarded in Stockholm and Oslo
Most Nobel Prizes—including Physiology or Medicine, Physics, Chemistry, Literature and the Prize in Economic Sciences—are decided and awarded in Stockholm by the respective Swedish institutions.
The Nobel Peace Prize is an exception: it is decided by the Norwegian Nobel Committee and awarded in Oslo. All prizes are presented annually on 10 December, the anniversary of Alfred Nobel’s death, with ceremonies in both capitals and laureate lectures preceding the events.
From tolerance biology to therapies
The laureates’ discoveries underpin clinical research that aims to modulate Tregs or enhance FOXP3 pathways to treat autoimmune conditions, improve transplant tolerance, and, in some contexts, fine‑tune immunity in cancer. Several trials are underway, but translating precision control of immune tolerance into routine care remains a medium‑term effort.
