The Nobel Prize for 2025 in Physiology or Medicine has been awarded to the trio Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi for “their discoveries concerning peripheral immune tolerance,” the Royal Swedish Academy of Sciences announced in Stockholm on Monday. The three researchers will split a prize of 11 million Swedish Kroner, which is around $1.17 million.
The laureates identified the immune system’s security guards, regulatory T cells, which prevent immune cells from attacking our own body, according to a press release by the academy.
Olle Kämpe, chair of the Nobel Committee, said, "Their discoveries have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases."
What were the discoveries?
Sakaguchi made the first key discovery in 1995. Many researchers at the time were convinced that immune tolerance only developed due to potentially harmful immune cells being eliminated in the thymus, through a process called central tolerance. Sakaguchi found that the immune system was more complex and discovered a previously unknown class of immune cells, which protect the body from autoimmune diseases.
In 2001, Mary Brunkow and Fred Ramsdell made the other key discovery. They found that a specific mouse strain was particularly vulnerable to autoimmune diseases because the mice had a mutation in a gene they named Foxp3.
Sakaguchi later linked the two discoveries. He proved that the Foxp3 governed the development of the immune cells, now called regulatory T cells, which he discovered in 1995. Regulatory T cells monitor other immune cells and ensure that our immune system tolerates our own tissues.
The discoveries launched the field of peripheral tolerance. Their work is now being used to develop new treatments for autoimmune diseases and cancer.
Last year, the Nobel Prize for Medicine was awarded to US scientists Victor Ambros and Gary Ruvkun for their discovery of microRNA and its key role in how multicellular organisms grow and live, helping explain how cells specialise into different types.
Who are the three laureates?
Shimon Sakaguchi, born in 1951, is an expert in immunology at Osaka University, Japan, and is a distinguished professor at the Immunology Frontier Research Center.
Mary E. Brunkow, 64, researches genomics and autoimmune diseases at the Institute for Systems Biology, Seattle.
Fred Ramsdell, 64, is a scientific advisor at Sonoma Biotherapeutics, a biotechnology company in San Francisco.
Brunkow and Ramsdell performed the research in the Seattle area for Celltech Chiroscience, a British-owned biotechnology company at the time.
Last year, the Nobel Prize in Physiology or Medicine went to Victor Ambros and Gary Ruvkun, who were recognised for their discovery of microRNA, a tiny class of RNA molecules that play a crucial role in determining how organisms mature and function.
The rest of the five Nobel Prizes in Physics, Chemistry, Literature, Peace, and the Memorial Prize in Economic Sciences will be announced throughout this week.