The 2025 Nobel Prize in Physiology or Medicine has been awarded to three groundbreaking researchers: Mary Blank, Fred Ramsdel, and Shimon Sakaguchi. They have made significant discoveries regarding a unique type of immune cell that prevents the immune system from attacking its own body.

“We have opened up an entirely new area in immunology,” stated Marie Warren Hellenius from the Karolinska Institute in Sweden.

T cells, a type of immune cell, are crucial for detecting and neutralizing harmful viruses and bacteria. These cells are continuously produced throughout a person’s life.

At times, newly formed T cell receptors may mistakenly target the body’s own proteins instead of those from viruses or bacteria, resulting in autoimmune disorders like type 1 diabetes and rheumatoid arthritis.

The body possesses mechanisms to eliminate autoreactive T cells, with newly generated ones migrating to the thymus for evaluation. This has long been believed to be the sole process for the removal of self-targeting T cells.

Yet in 1995, Sakaguchi, now at Osaka University, demonstrated through a mouse study that other circulating cells in the bloodstream must provide some form of protection against autoreactive T cells. When the thymus is removed post-birth, mice develop autoimmune conditions; however, this outcome is averted when healthy T cells are introduced. His research identified that these particular T cells feature the CD25 protein on their surface, thereby classifying them as CD25-regulated T cells.

Meanwhile, Blankku, currently affiliated with the Institute of Systems Biology in Seattle, and Ramsdell, who advises Sonoma Bitherapeutics in San Francisco, studied mouse strains predisposed to autoimmune diseases. In 2001, Brunkow and Ramsdell identified that these mice possess mutations in a gene located on the X chromosome, specifically FOXP3.

Individuals with mutations in this gene are particularly susceptible to autoimmune disorders due to a condition known as IPEX syndrome. In 2003, Sakaguchi connected these findings, showing that the FOXP3 gene is integral to the development of the CD25-regulated cells his team had identified. Many researchers previously remained skeptical of Sakaguchi’s assertions, according to Warren Hellenius. However, the findings from Brunkow and Ramsdell solidified the case.

The discovery of regulatory T cells could pave the way for improved treatments across a variety of conditions. Increasing the presence of regulatory T cells may help mitigate autoimmune responses that lead to diseases like type 1 diabetes. Conversely, reducing these cells can amplify the immune system’s response against cancer. Numerous clinical trials are currently being conducted.

“Their discoveries have been fundamental in understanding the workings of the immune system and explaining why serious autoimmune diseases don’t universally develop,” remarked Orkenpe, the chairman of the Nobel Committee, in a statement.