American scientists Mary Brunkow and Fred Ramsdell – and Shimon Sakaguchi from Japan – won the 2025 Nobel Prize in Physiology or Medicine on Monday for work shedding light on how the immune system spares healthy cells, creating openings for possible new autoimmune disease and cancer treatments, reports Reuters.
Their discoveries relate to peripheral immune tolerance, or “how we keep our immune system under control so we can fight all imaginable microbes and still avoid autoimmune disease”, said Marie Wahren-Herlenius, a rheumatology Professor at Sweden’s Karolinska Institute, the awarding body.
The institute said all three laureates brought to the fore so-called regulatory T cells, a class of white blood cells that act as the immune system's security guards that keep immune cells from attacking our own body.
Brunkow said she, Ramsdell and their colleagues had isolated a gene called FOXP3 that could be used as a marker for the cells.
“They’re rare, but powerful, and they’re critical for sort of dampening an immune response,” she added, describing the cells as a braking system that prevents the body’s immune system from tipping over into attacking itself.
Sakaguchi said he was surprised by the award because he felt any major recognition would have depended on more development advances.
“I used to think that some sort of reward may be forthcoming if what we have been doing will advance a little further and it will become more beneficial to people in clinical settings,” he said.
On how effective immunotherapy could be for cancer treatment in the future, he said: “I believe the time will come when cancer is no longer a scary disease, but a curable one.”
Winners of the award are selected by the Nobel Assembly of the Karolinska Institute, and receive a prize sum of $1.2m, as well as a gold medal presented by Sweden’s king.
Brunkow is senior programme manager at the Institute for Systems Biology in Seattle, while Ramsdell is scientific adviser at Sonoma Biotherapeutics in San Francisco. Sakaguchi is a Professor at Osaka University.
More than 200 trials on humans in progress
Jeffrey Bluestone, a colleague of Ramsdell and a co-founder with him of Sonoma Biotherapeutics, told Reuters his associate’s extraordinary contribution was finding the FOXP3 gene, initially in mice, that controlled the development of regulatory T cells. They described their findings in a paper in 2001.
“Those cells were the master regulators of the tolerance of the immune system,” said Bluestone.
Ramsdell could not be reached by Reuters – nor by Brunkow or Bluestone, with Bluestone saying he may be on a hiking trip in an area without phone reception.
After announcing the winners, the Karolinska Institute’s Thomas Perlmann said specific therapies had yet to win market clearance but more than 200 trials on humans involving regulatory T cells were ongoing.
Among companies in the early race, Ramsdell’s Sonoma Biotherapeutics is partly funded and supported by US drugmaker Regeneron to work on therapies against diseases, including inflammatory bowel disease.
Also targeting that condition, Quell Therapeutics has partnered with AstraZeneca. Other biotech firms exploring the approach include Bayer’s BlueRoc.
See more from MedicalBrief archives:
Cancer jab using immune system’s ‘killer’ cells on the cards – UK study
Landmark finding on cause of inflammatory bowel disease and immune disorders
Immunotherapy a safe alternative to surgery for early cancers – US trial
Immunotherapy before liver cancer surgery kills tumours – Mount Sinai clinical trial