Trio Wins 2025 Nobel Prize in Medicine for Contributions to the Discovery of Regulatory T Cells

A trio of scientists – Mary E. Brunkow, PhD, Fred Ramsdell, PhD and Shimon Sakaguchi, MD, PhD – were awarded the 2025 Nobel Prize in Physiology or Medicine on Monday for their groundbreaking discoveries relating to peripheral immune tolerance, ultimately leading to the discovery of regulatory T cells.

Sakaguchi first described these cells in 1995, challenging the prevailing view that immune tolerance only occurred through central tolerance through the elimination of potentially harmful immune cells in the thymus.

In 2001, Brunkow and Ramsdell discovered that mutations in the Foxp3 gene caused severe autoimmune disease in mice. The pair also found that mutations in the human equivalent of this gene cause a serious autoimmune disease, IPEX. Two years later, Sakaguchi established that the Foxp3 gene is the master regulator of regulatory T cell development and function, uniting the two lines of discovery.

Their landmark discoveries transformed scientific understanding of immune regulation and laid the foundation for ongoing research into autoimmune diseases, cancer immunotherapy and transplant tolerance.

“AABB congratulates Drs. Brunkow, Ramsdell and Sakaguchi on this remarkable achievement,” said AABB President Meghan Delaney, DO, MPH. “Their discoveries illustrate the power of scientific innovation to advance human health, informing new generations of biotherapies that hold tremendous promise for patients.”