U.S., Japan Researchers Share Nobel Prize for Unraveling Immune System’s Self-Control

The 2025 Nobel Prize announcements commenced today with the prestigious award in Physiology or Medicine, conferred upon scientists Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi for their groundbreaking research in peripheral immune tolerance, a mechanism that prevents the immune system from attacking the body’s own tissues.

Announced by the Nobel Committee at the Karolinska Institute in Stockholm, the trio was recognized for uncovering critical mechanisms that maintain immune balance and prevent autoimmune reactions. Their discoveries have significantly advanced the understanding of autoimmune diseases and opened new avenues for therapeutic interventions in conditions like type 1 diabetes, multiple sclerosis, and rheumatoid arthritis.

Shimon Sakaguchi, a researcher at Osaka University, was lauded for identifying a novel class of immune cells regulatory T cells (Tregs) that play a pivotal role in suppressing harmful immune responses. Meanwhile, Mary Brunkow and Fred Ramsdell, based in the United States, contributed by linking the Foxp3 gene to the development and function of these T cells, demonstrating how genetic mutations could lead to severe autoimmune disorders.

Their research highlighted regulatory T cells as key “guardians” against self-destructive immune attacks, a discovery that resolves a long-standing mystery in immunology. The Nobel Committee emphasized that their work forms the foundation for innovative treatments currently in clinical trials, aimed at managing autoimmune conditions, improving cancer immunotherapy, and reducing complications following stem cell transplants.

The laureates will share a prize of 11 million Swedish kronor (approximately USD 1.2 million) and receive their medals at the official ceremony on December 10 in Stockholm.

Following today’s announcement, the Nobel Prizes in Physics, Chemistry, Literature, Peace, and Economic Sciences will be revealed throughout the week. The Peace Prize is scheduled for Friday, while the Sveriges Riksbank Prize in Economic Sciences will be announced on October 13.