Science

Nobel Prize in medicine to Brunkow, Ramsdell and Sakaguchi for studies on the immune system

Their research, fundamental to the treatment of cancer and autoimmune diseases, paves the way for new therapies now in clinical trials.

by Francesca Cerati

6 October 2025

I vincitori del premio Nobel per la medicina 2025

3' min read

Translated by AI

Versione italiana

Key points

A discovery that changed modern medicine
A recognition already announced by science
From lab to patients
Three careers, one vision

3' min read

Translated by AI

Versione italiana

The 2025 Nobel Prize in Medicine was awarded to Mary E. Brunkow, Fred Ramsdell and Shimon Sakaguchi for their discoveries on the mechanisms of peripheral immune tolerance, a regulatory system that prevents the immune system from turning its weapons against the organism it is supposed to defend.

The research of the three scientists - two Americans and one Japanese - led to the identification of regulatory T-cells, true 'security guards' of the immune system. These cells act as sentinels that keep other immune cells at bay, preventing them from attacking healthy tissue. "Their discoveries have been decisive in understanding how the immune system works and why we do not all develop severe autoimmune diseases," said Olle Kämpe, chairman of the Nobel Committee.

A discovery that changed modern medicine

It all began in 1995, when Professor Shimon Sakaguchi of Osaka University, going against prevailing theories, demonstrated that immunological tolerance is not only based on the elimination of 'dangerous' cells in the thymus (so-called central tolerance), but also on a peripheral control mechanism. Sakaguchi identifies for the first time a population of T-cells with a suppressive function, capable of maintaining peace in the immune system.

If the body's defence system is an army, the regulatory T-cells are its military police: they control that the soldiers do not rebel and destroy their own bases.

In 2001 came the contributions of Mary Brunkow and Fred Ramsdell, who discovered the FOXP3 gene, responsible for the development and functioning of these cells. Studying mice suffering from serious autoimmune diseases, the two researchers show that a mutation in this gene leads to a collapse of the control system, paving the way for the organism's self-destruction. The same mutation, in humans, causes a rare and devastating childhood disease, the IPEX syndrome.

Two years later, Sakaguchi definitively linked the two lines of research: the FOXP3 gene is the 'central command' of regulatory T cells. Since then, their discovery has revolutionised immunology and opened up new therapeutic perspectives against autoimmune diseases, cancer and even in the field of organ transplantation.

A recognition already announced by science

Interestingly, for two of the awardees - Sakaguchi and Ramsdell - this is not the first time that the scientific community has recognised their discovery as revolutionary. Back in 2017, they had received, along with immunologist Alexander Rudensky, the Crafoord Prize in Polyarthritis, a prize awarded by the Royal Swedish Academy of Sciences for research into autoimmune diseases. That award, as many observers note today, was a prelude to the Nobel Prize.

From laboratory to patients

Today, thanks to their research, several groups around the world are experimenting with therapies capable of 'retraining' the immune system, using precisely the regulatory T cells to calm autoimmune reactions or, conversely, to deactivate them in tumours. Some of these treatments are already in clinical trials.

"This discovery has laid the foundation for a completely new field of medicine," said the Karolinska Institute board during the announcement. "Potential applications range from therapies for multiple sclerosis and type 1 diabetes to cancer treatments.

Three careers, one vision

Mary E. Brunkow, 64, is senior programme manager at the Institute for Systems Biology in Seattle. Fred Ramsdell, 65, is co-founder and scientific advisor of Sonoma Biotherapeutics in San Francisco. Shimon Sakaguchi, 74, is professor emeritus at the Immunology Frontier Research Center at Osaka University.

Together, they opened a window into the subtlest and most fascinating part of our immune system: the ability to distinguish between 'self' and 'non-self', between what must be destroyed and what must be saved.

Il ruolo dei linfociti T nel carcinoma mammario

As Sakaguchi told Japanese journalists: 'This is a great honour, but above all a victory for all those who believe that the human body also knows how to stop, not just how to attack.

The three scientists will split SEK 11 million, the same amount as in the last two years, or about EUR 1 million.