Nobel Prize in Medicine 2025: Brunkow, Ramsdell, Sakaguchi honored

TL;DR:

Nobel Prize in Medicine 2025 goes to Brunkow, Ramsdell, Sakaguchi.
They revealed how regulatory T cells prevent the body from attacking itself.
Work ties FoxP3 gene to immune control and autoimmune disease.
Findings shape trials for autoimmunity, cancer, and transplants.
Prize announced on 2025-10-06 in Stockholm, worth SEK 11 million.

Nobel Prize in Medicine 2025: how immune “brakes” changed care

The Nobel Assembly at Karolinska Institutet awarded the 2025 Nobel Prize in Physiology or Medicine to Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi on 6 October 2025. The trio is honored for discoveries that explain peripheral immune tolerance, the process that keeps the immune system from attacking the body. The prize is worth 11 million Swedish kronor.

What happened and why it matters

The laureates mapped a core control system in immunity. Sakaguchi identified a special T cell subset that prevents harmful self-reactivity. Brunkow and Ramsdell linked the gene FoxP3 to this control, showing that faults in FoxP3 trigger severe autoimmune disease. The Nobel Foundation calls these cells the immune system’s security guards.

Their work turned a concept into a clinical target. Trials now aim to boost or calm these cells to treat autoimmune conditions, reduce transplant rejection, and improve cancer care by lifting immune brakes when needed. Reports from Reuters, the Financial Times, and The Guardian all highlight this clinical horizon.

The science in brief

The early clue, 1990s

In the mid-1990s, Sakaguchi and colleagues described a population of T cells, later called regulatory T cells, that express markers like CD25 and control self-reactive responses. This finding challenged the view that thymus selection alone cleared dangerous T cells.

The genetic key, 2001

In 2001, Brunkow and Ramsdell connected mutations in FoxP3 to runaway autoimmunity in mice, then to a rare human disease, IPEX syndrome. The link made FoxP3 the master switch for regulatory T cell development. Sakaguchi later showed FoxP3 is essential for these cells to form and work.

From mechanism to medicine

With the pathway defined, teams began to test therapies that modulate regulatory T cells. The goal is simple. Turn them up to quiet autoimmunity or improve transplant tolerance, turn them down to unshackle anti-tumor immunity. Coverage today from multiple outlets underscores this two-way strategy.

Who the laureates are

Mary E. Brunkow, an American scientist, contributed core FoxP3 genetics work that tied gene defects to immune dysregulation and pointed to a master regulatory program. The Nobel summary credits her role in defining how the gene controls these cells.
Fred Ramsdell, an American immunologist, co-led the FoxP3 discoveries and helped translate them for therapy. He later advised companies developing T cell treatments, part of a broader push to apply the biology. News reports note his current advisory work.
Shimon Sakaguchi, a Japanese immunologist at Osaka University, discovered the regulatory T cell population and helped prove FoxP3 is its master regulator. His work established the concept of immune brakes in the periphery.

What it changes for patients

Autoimmune diseases

In type 1 diabetes, multiple sclerosis, and IBD, the immune system attacks the body. Expanding or boosting regulatory T cells could restore balance. Trials are testing cell therapies and biologics that increase these cells or enhance their function. The Nobel press material and global coverage highlight this near-term use.

Transplant medicine

Regulatory T cells may help reduce the need for lifelong broad immunosuppression, lowering infection and cancer risk. Researchers are working on donor-matched regulatory T cell infusions to improve graft survival. This is a key clinical pathway referenced in today’s reporting.

Cancer

Cancer immunotherapy often removes brakes on T cells. In some tumors, regulatory T cells crowd the tumor microenvironment and blunt attack. Strategies that target these cells could improve responses to checkpoint drugs. Outlets today describe this as a parallel track to autoimmunity work.

Key dates and context

6 October 2025. Prize announced in Stockholm, first of the Nobel week reveals. The Nobel Prize site confirms the time and details for this year’s schedule.
Prize sum. SEK 11 million shared by the three laureates. Official materials and multiple outlets report the amount and split.
Ceremony. Nobel awards are presented on 10 December 2025, the anniversary of Alfred Nobel’s death.

Background, in plain language

Your immune system is built to attack invaders. It also needs steady controls so it does not attack you. Regulatory T cells provide that control. They act like referees, calming harmful reactions while allowing defense to continue.

FoxP3 is the switch that creates these referees. When FoxP3 is broken, the body loses restraint. In mice, that causes lethal inflammation. In people, it causes IPEX syndrome, a rare but severe autoimmune disease. The laureates’ work connected these dots, giving medicine a new set of dials to turn.

What happens next

Expect more clinical trials that fine tune regulatory T cells by dose, timing, and route. Companies and academic centers are testing cell therapies made from a patient’s own regulatory T cells, along with drugs that encourage these cells to grow or work better. This roadmap is highlighted in today’s international coverage.

Fast facts table

Topic	What to know
Prize	Nobel Prize in Physiology or Medicine 2025
Laureates	Mary E. Brunkow, Fred Ramsdell, Shimon Sakaguchi
Field	Peripheral immune tolerance, regulatory T cells, FoxP3
Announcement	6 October 2025, Stockholm
Prize amount	SEK 11 million, shared equally
Clinical areas	Autoimmunity, transplantation, cancer

Why it matters

Autoimmune diseases affect hundreds of millions of people worldwide. Transplant patients face lifelong drug risks. Many cancers resist current immunotherapy. A clear map of immune brakes lets researchers design treatments that are more precise and safer. That map exists because of the work honored today.

What readers can watch for

Early results from cell therapy trials that infuse regulatory T cells in autoimmunity or kidney transplants.
Combinations of checkpoint drugs with approaches that alter regulatory T cells in tumors.
Genetic or molecular tools that boost FoxP3 activity without broad immune suppression.

Attribution and timing

The Nobel Foundation published the decision and scientific summary on 6 October 2025. Major outlets including Reuters, the Financial Times, and The Guardian reported the announcement the same day, with aligned details on the laureates and their work.

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