Mary E. Brunkow, Fred Ramsdell, Shimon Sakaguchi Named 2025 Nobel Laureates in Physiology or Medicine

Rockville, Md. (Oct. 6, 2025)—The American Physiological Society (APS) congratulates Mary E. Brunkow, PhD; Fred Ramsdell, PhD; and Shimon Sakaguchi, MD, PhD; the 2025 recipients of the Nobel Prize in Physiology or Medicine. This highest honor in modern science recognizes discoveries involving regulatory T cells and peripheral immune tolerance, the human immune system’s “security guards,” that prevent the body from attacking itself.  

“Their discoveries have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases,” Olle Kämpe, chair of the Nobel Committee, wrote in a statement.

Brunkow is senior program manager at the Institute for Systems Biology in Seattle. She earned her PhD in molecular biology from Princeton University. Together with Fred Ramsdell, in 2001 Brunkow discovered gene mutations that lead to autoimmune diseases, and dysfunction in T-cell responses.

Ramsdell is a scientific advisor at the San Francisco-based biotechnology company Sonoma Biotherapeutics and is research director at the Parker Institute for Cancer Immunotherapy. He received a PhD in microbiology and immunology from UCLA.

Sakaguchi is a distinguished professor at the Immunology Frontier Research Center at Osaka University, Japan. He received his MD and PhD from Kyoto University. In 1995, Sakaguchi discovered a new set of immune cells—now called regulatory T cells—in mice that protected the body from autoimmune diseases. In 2003, he linked his discovery with Brunkow’s and Ramsdell’s research.

The Nobel laureates’ work has provided a “new handle” for treating autoimmune diseases and organ transplants.

“The discovery of peripheral immune tolerance and regulatory T cells (T regs) presents a milestone in modern immunology,” APS Publications Committee Chair Wolfgang Kübler, PhD, FAPS, said in a statement. “T regs are essential for controlling normal immune responses. Breakdown of peripheral tolerance as a result of defective T reg development, stability or function is central to the pathogenesis of many well-known autoimmune diseases, but likely also contributes to numerous cardiovascular, renal, pulmonary or neurological pathologies which at first glance seem unrelated to autoimmunity.”

“The discoveries of this year´s Nobel Prize recipients not only lay the groundwork for new treatments in autoimmune diseases but have implications for a broad range of pathologies. This topic is reflected by APS’ cross-journal call for papers on women´s health and autoimmune diseases,” Kübler added.

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