Discoveries on “peripheral immune tolerance” pave the way for new treatments for cancer and autoimmune diseases
STOCKHOLM (AP) — Mary E. Brunkow, Fred Ramsdell and Dr. Shimon Sakaguchi have been awarded the 2025 Nobel Prize in Medicine for groundbreaking work that transformed our understanding of the human immune system. Their discoveries on peripheral immune tolerance laid the scientific foundation for new treatments targeting cancer, autoimmune disorders, and improving transplant outcomes.
The Nobel Assembly at the Karolinska Institute announced the award Monday, praising the laureates for launching “the field of peripheral tolerance,” which has already spurred the development of multiple therapies now in clinical trials.
Sakaguchi, 74, a distinguished professor at Osaka University’s Immunology Frontier Research Center, first identified a previously unknown type of T cell in 1995 — now known as regulatory T cells, or T-regs. These specialized cells act as the immune system’s “security guards,” curbing harmful overreactions from other T cells that could lead to autoimmune disease.
In 2001, Brunkow, 64, a senior program manager at the Institute for Systems Biology in Seattle, and Ramsdell, 64, a scientific adviser for Sonoma Biotherapeutics in San Francisco, identified a key mutation in the Foxp3 gene. This gene plays a central role in the development of T-regs and is linked to a rare autoimmune disease in humans.
Two years later, Sakaguchi connected the dots, demonstrating how Foxp3 controls T-reg development — a discovery that has reshaped modern immunology.
“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.
Thomas Perlmann, Secretary-General of the Nobel Committee, said Sakaguchi was “incredibly grateful” when reached by phone Monday morning. Voicemails were left for Brunkow and Ramsdell, who had not yet been reached at the time of the announcement.
The trio will share prize money totaling 11 million Swedish kronor (nearly $1.2 million USD).
The medicine prize is the first of the 2025 Nobel announcements, followed by physics on Tuesday, chemistry on Wednesday, literature on Thursday, the Nobel Peace Prize on Friday, and the economics prize on Oct. 13.
The award ceremony will take place on Dec. 10, the anniversary of Alfred Nobel’s death.