UCLA alumnus Fred Ramsdell wins 2025 Nobel Prize in physiology or medicine

Immunologist Frederick J. “Fred” Ramsdell, who earned his doctorate in microbiology and immunology from UCLA in 1987, has been awarded the 2025 Nobel Prize in physiology or medicine for his groundbreaking work on the human immune system.

Ramsdell, a scientific advisor with Sonoma Biotherapeutics in San Francisco, shares the prize with Mary Brunkow of the Institute for Systems Biology in Seattle and Shimon Sakaguchi of Osaka University in Japan for their collective research on how immune cells known as regulatory T cells prevent the immune system from harming the body’s own tissues.  

Their discoveries, the Nobel committee noted, have laid the foundation for a new field of research known as peripheral immune tolerance and have spurred the pursuit of regulatory T cell–centered therapeutics in areas like cancer, autoimmune disease and stem cell transplantation. There are currently more than 200 ongoing clinical trials based on their research.

“Fred Ramsdell’s research on the immune system has transformed our understanding of autoimmune diseases and led to treatments that are saving lives around the world,” said UCLA Chancellor Julio Frenk. “From improving care for conditions like multiple sclerosis to advancing cancer therapies, his work is driving medical breakthroughs that will shape the future of human health. I hope Bruins everywhere take pride in this well-deserved global recognition.

“At a time of unprecedented challenges to research funding, once again the United States leads the way in medical breakthroughs recognized by the Nobel Prize,” Frenk added.

Regulatory T cells and how they develop

Sakaguchi first identified the immune system’s regulatory T cells, or “T-regs,” in 1995, showing that this specialized subclass of T cells acts as a kind of peacekeeper, patrolling the activity of other immune cells in the body and damping down any overactive immune responses that could lead to autoimmune diseases.

In 2001, Ramsdell and Brunkow made another crucial discovery when they found that a specific mutation to a gene they named Foxp3 made the mouse strain they were studying particularly vulnerable to fatal autoimmune diseases. Not long after, they demonstrated that similar mutations caused a devastating autoimmune disease known as IPEX syndrome in humans.

Two years later, both Sakaguchi and Ramsdell, along with a colleague, described how the Foxp3 gene that Ramsdell and Brunkow discovered was directly responsible for governing the body’s development of regulatory T cells — shining a light on how the mutation interfered with that production.

“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.

At UCLA and beyond

After earning a bachelor’s degree in biochemistry and cell biology from UC San Diego, Ramsdell came to UCLA in 1983 to study microbiology and immunology at UCLA’s medical school under the mentorship of Sidney Golub, now a professor at UC Irvine. In 1995, the microbiology and immunology program merged with the molecular genetics program in the UCLA College Division of Life Sciences.

“I fell in love with immunology in college,” Ramsdell said after receiving the prestigious Crafoord Prize in Polyarthritis from the Royal Swedish Academy of Sciences in 2017. “It touches so many aspects of our biology that I felt like it was an important thing to work on.”

Following his 1987 Ph.D. at UCLA, Ramsdell went on to a fellowship with the National Institutes of Health before joining the biopharmaceutical company Immunex, where his research focused on T cell activation and tolerance and gene discovery. He then established an immunology program at the biotechnology company Darwin Molecular. Ramsdell subsequently held positions at ZymoGenetics and Novo Nordisk and was chief scientific officer at the Parker Institute for Cancer Immunotherapy. He currently serves on the scientific advisory board for Sonoma Biotherapeutics.

What award? Ramsdell was off the grid in the Rockies when the call came

At the time of the Nobel Prize announcement, Ramsdell was on a trek with his wife in the Rocky Mountains, without cellphone reception. He didn’t find out about the honor until nearly 12 hours had passed. Sonoma Biotherapeutics issued a statement that Ramsdell “was living his best life and was off the grid on a preplanned hiking trip.”

“I certainly didn’t expect to win the Nobel Prize,” he told the New York Times from a hotel in Montana once he’d regained reception. “It never even crossed my mind.

“I was just grateful and humbled by getting the award, super happy for the recognition of the work in general and just looking forward to sharing this with my colleagues, as well.” 

► Read the full story on Ramsdell’s “missed” Nobel phone call in the New York Times.

In addition to Ramsdell, eight UCLA graduates have won the Nobel Prize: Ardem Patapoutian (physiology or medicine, 2021), Randy Schekman (physiology or medicine, 2013), Richard Heck (chemistry, 2010), Elinor Ostrom (economic sciences, 2009), William Sharpe (economic sciences, 1990), Bruce Merrifield (chemistry, 1984), Glenn Seaborg (chemistry, 1951) and Ralph Bunche (peace, 1950).

Eight UCLA faculty members have been named Nobel laureates: Willard Libby (chemistry, 1960), Julian Schwinger (physics, 1965), Donald Cram (chemistry, 1987), Paul Boyer (chemistry, 1997), Louis Ignarro (physiology or medicine, 1998), Lloyd Shapley (economics, 2012), J. Fraser Stoddart (chemistry, 2016) and Andrea Ghez (physics, 2020). Stoddart was a Northwestern University faculty member when he received the honor, but much of the work for which he was recognized was conducted at UCLA from 1997 to 2008.