Immunologist Frederick J. “Fred” Ramsdell has been awarded the 2025 Nobel Prize in physiology or medicine for his work on the human immune system. Ramsdell earned his undergraduate degree from UC San Diego and completed his doctorate in microbiology and immunology at UCLA.
Ramsdell, currently a scientific advisor with Sonoma Biotherapeutics in San Francisco, shares the Nobel Prize with Mary Brunkow of the Institute for Systems Biology in Seattle and Shimon Sakaguchi of Osaka University in Japan. The three scientists were recognized for their research into regulatory T cells, which help prevent the immune system from attacking the body’s own tissues.
According to the Nobel committee, their discoveries have led to a new area of study called peripheral immune tolerance and encouraged development of therapies targeting regulatory T cells for diseases such as cancer, autoimmune disorders, and organ transplantation. Their findings have contributed to more than 200 ongoing clinical trials focused on these applications.
“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.
Sakaguchi first identified regulatory T cells (T-regs) in 1995 as key controllers that keep other immune cells from causing autoimmune disease. In 2001, Ramsdell and Brunkow discovered that mutations in a gene called Foxp3 made mice susceptible to fatal autoimmune illnesses. They later showed similar mutations cause IPEX syndrome—a severe autoimmune disorder—in humans. By 2003, Sakaguchi, Ramsdell, and colleagues described how Foxp3 directly governs regulatory T cell development.
“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.
After receiving his Ph.D., Ramsdell joined NIH as a fellow before moving into biotechnology roles at Immunex (focusing on T cell activation), Darwin Molecular (establishing an immunology program), ZymoGenetics, Novo Nordisk, and serving as chief scientific officer at Parker Institute for Cancer Immunotherapy. He is now on Sonoma Biotherapeutics’ advisory board.
Ramsdell joins eight other UCLA alumni who have won Nobel Prizes across disciplines including physiology or medicine, chemistry, economics, and peace. Eight UCLA faculty members have also received Nobel honors over past decades.
