Princeton University Alumna Mary Brunkow was awarded the 2025 Nobel Prize in Medicine.
Along with Fred Ramsdell and Shimon Sakaguchi, Brunkow was awarded for discoveries concerning peripheral immune tolerance that prevents the immune system from harming the body. She is a senior program manager at the Institute for Systems Biology in Seattle and received her Ph.D. from Princeton in 1991 in molecular biology.
“Peripheral immune tolerance” refers to a subtle but vital component of the human immune system. This is a piece that balances the body’s need to fight off external threats without attacking internal systems.
It was once thought that this balance was achieved through “central immune tolerance,” in which new T cells that could attack the host are weeded out in the thymus before they are unleashed upon the body. However, the trio added a new layer to this theory.
Chair of the Nobel Committee Olle Kämpe praised their work.
“Their discoveries about how the immune system is kept in check have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases,” he said.
The initial discovery, from Sakaguchi, revealed an unknown class of immune cells that protect against autoimmune diseases: regulatory T cells. Brunkow and Ramsdell moved that work forward by identifying a mutated gene linked to an autoimmune disease.
Two years later, Sakaguchi showed that the Foxp3 gene controls the development of regulatory T cells, which prevent other T cells from mistakenly attacking their own host. Regulatory T cells also signal to the immune system when it can stand down after it fights off invading viruses or bacteria.
Princeton President Christopher Eisgruber also praised Brunkow.
The trailblazing achievements illustrate the power of high-quality scientific research to improve human health and change our world for the better,” he said.
