The Nobel Prize in Medicine Honors Research on Immune System Control

The 2025 Nobel Prize in Medicine was awarded on Monday to American researchers Mary E. Brunkow and Fred Ramsdell, along with Japanese scientist Shimon Sakaguchi, for their work on how the body regulates its immune system.

The Nobel committee announced that the award recognizes their “discoveries concerning peripheral immune tolerance.”

“This year’s Nobel Prize in Physiology or Medicine focuses on how we control our immune system to combat a wide array of microbes while avoiding autoimmune diseases,” explained Marie Wahren-Herlenius, a professor at the Karolinska Institute.

“The powerful immune system must be regulated; otherwise, it may attack our own organs,” emphasized the Nobel committee.

The laureates have “identified the guardians of the immune system, the regulatory T cells, which prevent immune cells from attacking our own body,” it added.

As a result, they “have laid the foundations for a new field of research and led to the development of new treatments, for instance, for cancer and autoimmune diseases,” it further noted.

Regulatory T Cells

Shimon Sakaguchi, 74, an immunology researcher at Osaka University, made the first breakthrough in this area in 1995.

At that time, many researchers believed that immune tolerance developed solely through the elimination of potentially dangerous immune cells in the thymus, an organ located in the upper left part of the abdomen near the stomach, through a process known as “central tolerance.”

The Japanese researcher demonstrated that the immune system is more complex and “discovered a previously unknown class of immune cells that protects the body from autoimmune diseases,” according to the jury.

Mary E. Brunkow, born in 1961, and Fred Ramsdell, 64, made another key discovery in 2001 when they showed how a certain type of mouse was particularly susceptible to autoimmune diseases. “They discovered that these mice had a mutation in a gene they named Foxp3,” stated the jury.

They also highlighted that mutations in the human equivalent of this gene cause a severe autoimmune disease known as IPEX.

Two years later, Shimon Sakaguchi successfully linked his discoveries with those of Brunkow and Ramsdell, demonstrating that the Foxp3 gene governed 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.”

Mary E. Brunkow works at the Institute for Systems Biology in Seattle, an independent research organization, while Fred Ramsdell is at Sonoma Biotherapeutics in San Francisco, a biotechnology company.

Fragile American Research

Researchers from major American institutions are once again shining with this Nobel Prize in Medicine, but budget cuts implemented by President Donald Trump are likely to fuel the debate over the risk of weakening American research in the medium term.

Last year, the Nobel Prize in Medicine was awarded to Americans Victor Ambros and Gary Ruvkun for their discovery of microRNAs, a new class of tiny RNA molecules playing a crucial role in regulating gene activity.

The 2025 Nobel laureates might use their global platform to raise concerns about the announced reductions in funding for American scientific research.

Since January, the National Institutes of Health (NIH), the agencies overseeing medical research in the United States, have canceled 2,100 research grants, totaling approximately $9.5 billion, according to the independent database Grant Watch.

The Nobel Prize includes a diploma, a gold medal, and a check for 11 million Swedish kronor (nearly one million euros).