American scientists win Nobel Prize for immune system discovery

West Coast scientists Mary E. Brunkow and Fred Ramsdell have won the 2025 Nobel Prize in physiology or medicine, according to a Monday release from the Nobel Foundation. The pair and their partner, Japanese scientist Shimon Sakaguchi, won the award for their discoveries on how the human immune system regulates itself. Brunkow serves as a senior program manager at the Institute for Systems Biology in Seattle, Wash., Ramsdell co-founded Sonoma Biotherapeutics in San Francisco, and Sakaguchi is an immunologist at Japan’s Osaka University.

The trio identified regulatory T cells that stop immune cells from attacking the body’s own organs, and those discoveries improved scientific understanding of the immune systems’ function and why all humans don’t develop serious autoimmune diseases, explained Olle Kämpe, chair of Nobel committee that awarded the prize. The discoveries ultimately launched the field of peripheral tolerance, kickstarting the development of medical treatments for cancer and autoimmune diseases, the committee added.

Last year, the Sweden-based committee honored two scientists from Harvard University and the University of Massachusetts Medical School with the physiology or medicine prize for discovering tiny RNA molecules involved in gene regulation.

When will the other Nobel prizes be announced? Various Nobel Committees will honor consequential contributions to the field of physics on Tuesday and contributions to chemistry on Wednesday. The 2025 literature prize will be announced on Thursday, followed by the peace prize on Friday, then the economic sciences memorial prize the following Monday. 

Dig deeper: Read my previous report on Israeli Prime Minister Benjamin Netanyahu nominating President Donald Trump for the Nobel Peace Prize earlier this year.