Fred Ramsdell

Fred Ramsdell (born December 4, 1960, Elmhurst, Illinois, U.S.) is an American biologist who was awarded the 2025 Nobel Prize for Physiology or Medicine for his work on the immune system. He shared the prize with American biologist Mary E. Brunkow and Japanese immunologist Shimon Sakaguchi.

Ramsdell received a doctorate in microbiology and immunology from the University of California, Los Angeles. When he received the Nobel Prize, he was a scientific adviser for Sonoma Biotherapeutics in San Francisco.

In the 1990s Ramsdell and Brunkow worked at Celltech Chiroscience, a company that was developing drugs for autoimmune diseases, in which the immune system fights against the body’s own cells. They were studying a variety of mice, called scurfy, that had such a disease. They identified the gene responsible for the disease and found that the same gene in humans was responsible for an autoimmune disease. Sakaguchi and others discovered that the gene was responsible for the development of regulatory T cells, which control the body’s immune reactions by stopping other T cells from attacking normal cells.