Nobel prize for medicine goes to trio for work on immune tolerance

The Nobel Prize for Physiology or Medicine in 2025 went to three researchers – Mary Brunkow, Fred Ramsdell and Shimon Sakaguchi – who discovered a type of immune cell that helps prevent the immune system from attacking.

“He sparked a brand new field in immunology,” said Marie Wahren-Herlenius at the Karolinska Institute in Sweden.

Immune cells called T cells play a key role in immunity by entering invasive viruses and bacteria via receptors on their surface. New types of T cells are generated throughout our lives.

Sometimes, newly generated T cell receptors seize our own proteins instead of our own viral or bacterial proteins, which can cause conditions such as type 1 diabetes and rheumatoid arthritis.

The body has a system to eliminate self-reactive T cells, with newly formed T cells traveling with thymus for a test. It has been believed for a long time as the only way for self-targeted T cells.

But in 1995, Sakaguchi, now at the University of Osaka in Japan, showed in mouse experiences that certain other cells circulating in the blood circulation were also to protect self-reactive T cells. If the mice thymus is removed after birth, according to Sakaguchi, animals develop autoimmune conditions. But if the health of healthy mice are injected there, this is prevented. His team found that specific T cells responsible for this have a protein called CD25 on their surface, and called them the regulatory T cells of the CD25.

Meanwhile, Brunkow, now at the Institute of Systems Biology in Seattle, Washington and Ramsdell, advisor to Sonoma Biotherapeutics in San Francisco, California, studied mouse strain which is particularly likely to obtain autoimmune conditions. In 2001, Brunkow and Ramsdell discovered that these mice have a mutation in a gene on the X chromosome called Foxp3.

People with mutations in this gene are also particularly likely to obtain an autoimmune disease, due to a condition known as IPEX syndrome. In 2003, Sakaguchi showed that these two discoveries are linked – the Foxp3 Gene plays a key role in the development of CD25 regulatory cells that her team has discovered. Many researchers were skeptical about the previous claims of Sakaguchi, said Wahren-Herlenius. But the work of Brunkow and Ramsdell won the case.

The discovery of regulatory T cells could lead to better treatments for a wide range of conditions. On the one hand, increasing the number of regulatory T cells could help remove autoimmune reactions that cause conditions such as type 1. on the other, the reduction in the number of regulatory T cells could increase the immune response against cancer. A number of clinical trials are now underway.

“Their discoveries were decisive for our understanding of the functioning of the immune system and why we do not all develop serious autoimmune diseases,” said Olle Kämpe, president of the Nobel Committee, in a press release.