Nobel Prize for the "Brakes" of Immunity: Science Tackling Cancer and Autoimmunity - American and Japanese Scientists Awarded the Nobel Prize in Medicine

The Concept of "Stopping the Runaway of Immunity" Reaches the Nobel Prize

October 6, 2025 (Stockholm). The Nobel Prize season opened with the Physiology or Medicine Prize, highlighting the "defensive power" in immunology. The laureates are Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi. The award was given for elucidating the mechanism of "peripheral immune tolerance," a key to preventing the immune system from attacking itself. The central player is the regulatory T cell (Treg), now a textbook keyword. The identification of the FOXP3 gene, essential for the existence and development of these cells, has broadened the horizons of medical treatment from autoimmune diseases to cancer therapy.NobelPrize.org

What the Three Discovered: Treg and FOXP3

Traditionally, the immune system was thought to rely on "central immune tolerance" in the thymus to eliminate "self-reactivity." However, the reality of living organisms is more complex, with mechanisms to suppress runaway reactions even in the periphery. In the 1990s, Sakaguchi conceived the existence of a cell group that suppresses autoimmunity, defining Treg as CD25-positive CD4-positive T cells and establishing the concept. Subsequently, Brunkow and Ramsdell tracked the causative gene of the "scurfy" mouse, which exhibits lethal lymphoproliferation, identifying FOXP3 as a transcription factor essential for Treg differentiation. FOXP3 is also linked to the rare human disease IPEX syndrome, becoming a core marker of Treg.NobelPrize.org

From Lab to Bedside: Clinical Implications

This rediscovery of the "immune brake" extends beyond basic research. Globally, there are over 200 clinical trials targeting Treg, with corporate alliances tackling inflammatory bowel diseases and more. Companies like Sonoma Biotherapeutics, involving Ramsdell, Quell Therapeutics in partnership with AstraZeneca, and Bayer/BlueRock are beginning to establish industry pipelines. As of the award announcement, no specific therapies have received regulatory approval, but applied research is accelerating.Reuters

The Moment of Award: Each Laureate's "Surprise"

In a press conference in Osaka, Sakaguchi candidly expressed his surprise at the "early" recognition, saying, "I thought it would be evaluated after it became more useful in clinical practice." During the conference, he received a congratulatory call from Prime Minister Shigeru Ishiba. Brunkow was awakened by news photographers at her home in Seattle and initially ignored the Swedish phone number, thinking it was "spam." Ramsdell was backpacking in the mountains, learning of the award while off-grid, adding to the Nobel Prize's charm of slipping into scientists' "everyday" lives.Reuters

Reactions on Social Media: #Treg #ImmuneTolerance Goes Viral

Immediately after the announcement, the official account of X (formerly Twitter) announced the award, with international societies and research institutions posting congratulations. The American Association of Immunologists (AAI) praised Sakaguchi's achievements, and in Japan, "regulatory T cells" and "Shimon Sakaguchi" trended. Publishers and science museum accounts posted easy-to-understand explanatory threads, with voices expressing hope for educational material development. Amid the celebrations, there was notable interest in clinical applications, with questions like "When will it reach autoimmune patients?" and "How will it be differentiated in cancer treatment?"X (formerly Twitter)

Typical Voices
・"It's an era where not only 'attacking immunity' but also 'suppressing immunity' takes the spotlight."
・"It feels like high school biology textbooks will be updated all at once."
・"Autoimmunity and cancer, tuning the accelerator and brake is key."
(Summary by the editorial team)

What the Award Means for the "Next Decade"

The therapeutic use of Treg has a dual nature. In autoimmunity and transplantation, Treg is enhanced/introduced, while in cancer, the "brake" is removed to activate immunity. This precise tuning directly connects to not only biopharmaceuticals but also cell therapy (e.g., ex vivo expansion and administration of Treg cells). Barriers to clinical introduction include the specificity of target markers, long-term safety, and manufacturing scale. However, with FOXP3 as a "central axis," the platformization across diseases is becoming a reality.NobelPrize.org

The Nobel Prize as a Scientific Culture

This award is a quintessential example of the structure where "fundamentals drive clinical applications." The diligent exploration of the fundamental question in immunology—"How is self/non-self discrimination maintained?"—opens the door to extensive medical applications decades later. The prize money is 11 million Swedish kronor. The award ceremony will be held on December 10, as usual, on the anniversary of Nobel's death.NobelPrize.org

To Learn More

Comprehensive and specialized journals in natural sciences provide clear summaries of the "history and present" of Treg. From the beginnings of research, gene identification in mice, human disease associations, to the current state of clinical trials—reading alongside this article should make the continuity and speed of research advancements clearer.Nature