Three scientists — Americans Mary Brunkow and Fred Ramsdell, and Japan’s Shimon Sakaguchi — have been awarded the 2025 Nobel Prize in Physiology or Medicine for groundbreaking discoveries about immune system precision. Their work explains how the body’s immune system spares healthy cells while fighting harmful microbes, paving the way for new treatments for autoimmune diseases and cancer.
The Nobel committee said the research focuses on peripheral immune tolerance, which determines “how we keep our immune system under control.” The discoveries highlight the role of regulatory T cells — special immune cells that act as security guards, preventing the body from attacking its own tissues.
Experts described the findings as a major step toward understanding immune system precision. The discoveries have opened doors to potential therapies for conditions like rheumatoid arthritis, inflammatory bowel disease, and certain cancers.
Brunkow is a senior program manager at the Institute for Systems Biology in Seattle, while Ramsdell serves as a scientific adviser at Sonoma Biotherapeutics in San Francisco. Sakaguchi, a professor at Osaka University, expressed gratitude for the recognition, calling it “a tremendous honor.”
The Nobel Assembly at Sweden’s Karolinska Institute awards the prize, which includes 11 million Swedish crowns (about $1.2 million) and a gold medal. The committee said over 200 human trials are underway to explore how regulatory T cells can be used in medicine — a promising sign of how immune system precision could revolutionize healthcare.
Several biotech firms, including Sonoma Biotherapeutics, Quell Therapeutics, and Bayer’s BlueRock, are developing treatments based on this discovery. These companies aim to harness immune system precision to design therapies that restore balance without weakening natural defenses.
Medicine traditionally opens the Nobel Prize season, followed by awards in physics, chemistry, literature, peace, and economics. The winners will be honored in Stockholm in December, continuing a century-old tradition celebrating excellence in science and innovation.
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