US-Japanese Trio Wins Medicine Nobel: Who Are Mary Brunkow, Fred Ramsdell & Shimon Sakaguchi?

Last Updated:October 06, 2025, 17:11 IST

The US-Japanese trio's discoveries have been decisive in understanding how the immune system functions and why we do not all develop serious autoimmune diseases

(L-R) Mary E Brunkow, Fred Ramsdell and Shimon Sakaguchi are the winners of the 2025 Nobel Prize in Physiology or Medicine. (Image: Claudio BRESCIANI/AFP)

The 2025 Nobel Prize in physiology or medicine has been awarded to the US-Japanese trio of Mary E Brunkow, Fred Ramsdell and Shimon Sakaguchi “for their discoveries concerning peripheral immune tolerance".

Simply put, they have won the Nobel for research into how the immune system is kept in check. Their discoveries have been decisive in understanding how the immune system functions and why we do not all develop serious autoimmune diseases, the Nobel jury said.

Here’s a look at who they are:

SHIMON SAKAGUCHI

Japan’s Shimon Sakaguchi, 74, found a new class of T cells – a key discovery – when he was all but swimming against the tide in 1995. 

According to the website of The Nobel Prize, at the time, many researchers were convinced that immune tolerance only developed due to potentially harmful immune cells being eliminated in the thymus, through a process called central tolerance.

But Sakaguchi showed that the immune system is more complex and discovered a previously unknown class of immune cells, which protect the body from autoimmune diseases, the website stated.

Sakaguchi is affiliated with the University of Osaka in Japan as a principal investigator in the experimental immunology department at the Immunology Frontier Research Center (iFReC) in the University of Osaka.

His specialisation is in the field of immunology (immunological tolerance and autoimmune diseases). Born in 1951 in Japan’s Shiga prefecture, he completed his education from Kyoto University, receiving an MD in 1976 and PhD in 1982. He has a postdoctoral degree from Johns Hopkins University and Stanford University as a Lucille P Markey scholar. 

MARY BRUNKOW AND FRED RAMSDELL

The Americans, Mary Brunkow and Fred Ramsdell, gained decisive insights into how autoimmune diseases arise.

The Nobel website said they made another key discovery in 2001, when they presented the explanation for why a specific mouse strain (named scurfy) was particularly vulnerable to autoimmune diseases. They had discovered that the mice have a mutation in a gene that they named Foxp3 and also showed that mutations in the human equivalent of this gene cause a serious autoimmune disease, IPEX, it said.

It said two years after this, Sakaguchi was able to link these discoveries and proved that the Foxp3 gene governs the development of the cells he identified in 1995. These cells, now known as regulatory T cells, monitor other immune cells and ensure that our immune system tolerates our own tissues, it added.

Brunkow, born in 1961, is affiliated with the Institute for Systems Biology (ISB), Seattle, in the US as a senior programme manager. She describes herself in the organisation’s website as having joined ISB in 2009, and has since “worked to support a number of different projects: Family Genomics in a wide variety of disease areas, the systems biology of Lyme disease, sepsis biomarkers, and scientific wellness".

Her expertise is molecular biology, molecular genetics, and genomics. Apart from 10 years of experience in the biotech industry, she has a bachelor’s degree in molecular and cellular biology from the University of Washington, and an MS and PhD in molecular biology from Princeton University.

With nearly three decades of experience as a veteran biotechnology leader in immunology, 64-year-old Ramsdell is affiliated with Sonoma Biotherapeutics, San Francisco, in the US.

During a fellowship at the Institutes of Health (NIH), Ramsdell studied T cell activation and tolerance. “A major part of his work included the identification and characterisation of various tumour necrosis factors and their receptors, proteins that play an important role in inflammation and immunity," stated his profile with Parker Institute for Cancer Immunotherapy.

He has a doctoral degree in microbiology and immunology from the University of California in Los Angeles and a bachelor’s degree in biochemistry and cell biology from the University of California in San Diego.

(With agency inputs)

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