2025 Nobel Prize in Medicine Honors Discoveries Made Possible by Mice

The 2025 Nobel Prize in Physiology or Medicine recognizes Mary E. Brunkow, PhD; Fred Ramsdell, PhD; and Shimon Sakaguchi, MD, PhD, for discovering how the immune system prevents the body from attacking its own tissues and organs — a breakthrough that reshaped modern immunology.

In 1995 Sakaguchi at the University of Osaka in Japan studied the role of the thymus organ in immune response in mice. He discovered that the thymus does not eliminate all self-reactive T cells that can attack the body in mice. He realized a new type of T cell produced by the thymus, called regulatory T cells, actively suppresses attacks from harmful T cells.

In 2001 Brunkow and Ramsdell, who both worked for the British-owned biotech Celltech Chiroscience outside of Seattle at the time, studied a strain of “scurfy” mice that developed severe autoimmune disease. They identified a mutation in the gene Foxp3. They also showed that mutations in the human equivalent of this gene cause a serious autoimmune disease, IPEX.

In 2003 Sakaguchi showed that that the Foxp3 gene governs the development of the cells he identified in 1995, the regulatory T cells, or Tregs.

Together, their work explained how the immune system maintains balance, preventing autoimmune diseases and conditions like Type 1 diabetes and multiple sclerosis, and opening the door to new treatments in cancer immunotherapy and transplantation. There are more than 200 clinical trials underway that build on their research. (SEE MORE ABOUT NOBEL-WINNING ANIMAL RESEARCH HERE.)

This Nobel Prize highlights an important truth: Animal research drives medical advancement. Studies with mice revealed the genetic key to immune tolerance, providing knowledge that continues to improve and save human lives.

Read the Nobel Prize press release here: https://www.nobelprize.org/prizes/medicine/2025/press-release/.