The 2025 Nobel Prize in Physiology or Medicine has been awarded to Shimon Sakaguchi, Alexander Brunkow, and Ethan Ramsdell for their pioneering work on regulatory T cells (T-regs) and the mechanisms of peripheral immune tolerance.

The Nobel Committee highlighted that Sakaguchi first discovered a previously unknown T cell subtype in 1995, now known as regulatory T cells, which play a key role in preventing overactive immune responses. Later, in 2001, Brunkow and Ramsdell identified a mutation in the Foxp3 gene, linked to a rare human autoimmune disease. Sakaguchi then connected the findings, demonstrating that Foxp3 controls the development of T-regs, which act as “security guards” to regulate overreactive T cells.

According to the Karolinska Institute, their work has opened a new field in immunology, allowing researchers worldwide to explore therapies for autoimmune diseases and cancer. “Their discoveries have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases,” said Olle Kämpe, chair of the Nobel Committee.

Thomas Perlmann, Secretary-General of the Nobel Committee, described Sakaguchi as “incredibly grateful” when contacted by phone about the honor. The award marks the first of the 2025 Nobel announcements, with the Physics Prize set for Tuesday, Chemistry on Wednesday, Literature on Thursday, Peace on Friday, and the Economics Prize on October 13.

The Nobel Prize ceremony will take place on December 10, commemorating the anniversary of Alfred Nobel’s death, the Swedish industrialist and inventor of dynamite who founded the prestigious awards in 1896.