Medicine Nobel awarded to trio for work on human immune system

Stockholm: The Nobel Prize for 2025 in Physiology or Medicine goes to 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 (October 6, 2025).

The laureates identified the immune system’s security guards, regulatory T cells, which prevent immune cells from attacking our own body. “Their discoveries have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases,” said Olle Kämpe, chair of the Nobel Committee.

In 1995 when researchers believed that immune tolerance developed through a process called ‘central tolerance’, Shimon Sakaguchi discovered a previously unknown class of immune cells, which protect the body from autoimmune diseases.

Mary Brunkow and Fred Ramsdell made another key discovery in 2011.

They discovered that a specific mouse strain was particularly vulnerable to autoimmune diseases, because they have a mutation in a gene which they named Foxp3. They also showed that mutations in the human equivalent of this gene cause a serious autoimmune disease, IPEX. Two years later, Sakaguchi linked these discoveries and proved that the Foxp3 gene governs the development of the cells that 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, who earned her doctorate from Princeton University, is a Senior Program Manager at the Institute for Systems Biology, Seattle. Fred Ramsdell is Scientific Advisor at Sonoma Biotherapeutics, USA, while Shimon Sakaguchi is a Distinguished Professor at the Immunology Frontier Research Center, Osaka University, Japan. Last year, the Medicine Nobel was jointly awarded to Victor Ambros and Gary Ruvkun for the discovery of microRNA and its role in post-transcriptional gene regulation.