Celebrating the Nobel Prize in Physiology or Medicine 2025 Awarded to Professor Shimon Sakaguchi
We extend our heartfelt congratulations to Professor Shimon Sakaguchi, Specially Appointed Professor at the Immunology Frontier Research Center (IFReC), Osaka University, for being awarded the 2025 Nobel Prize in Physiology or Medicine for his discovery of regulatory T cells (Treg)-a key mechanism that maintains immune tolerance-and for elucidating their molecular basis.
After returning to Japan from the United States, Professor Sakaguchi continued his research as a PRESTO Researcher of the Research Development Corporation of Japan (currently the Japan Science and Technology Agency, JST), working at a laboratory in the RIKEN Life Science Tsukuba Research Center. In 1995, he was the first in the world to report that CD4+CD25+ T cells play a crucial role in suppressing autoimmune responses (J. Immunol., 155:1151–1164). It is a great honor and source of pride for us that such a historic discovery was made at what is now the RIKEN Tsukuba Campus.
According to the official Scientific Background of the Nobel Committee (2025), this 1995 study is described as “the renaissance of suppressor T cell research.” This seminal work paved the way for the discovery of the Foxp3 gene (Brunkow et al., 2001) and the establishment of Treg differentiation mechanisms (Hori, Nomura, and Sakaguchi, 2003), which together have revolutionized our understanding and treatment of autoimmune diseases, allergies, and cancer immunology.
Professor Sakaguchi’s pioneering discoveries were all derived from meticulous immunological analyses using laboratory mice, reaffirming the scientific and societal importance of animal experimentation. To understand the complex physiological process of immune homeostasis, experimental animal models that can reproduce systemic immune networks are indispensable. This Nobel Prize highlights the essential role of such refined research in advancing biomedical science and communicating its value to society.
The RIKEN BioResource Research Center (BRC), serving as the core facility for the National BioResource Project (NBRP) for experimental mice, maintains and distributes a wide variety of mouse strains, including genetically engineered strains developed in Japan. In Professor Sakaguchi’s recent studies, the Rbpj-floxed mouse (RBRC01071)-generous deposit by Professor Tasuku Honjo, Nobel Laureate in 2018—was utilized to achieve groundbreaking results (Nature, 642:191–200, 2025) that may lead to new therapeutic strategies for autoimmune diseases.
We take great pride in the fact that research conducted here in Tsukuba has contributed to discoveries that have reshaped global immunology. We once again offer our sincere congratulations to Professor Sakaguchi on this distinguished honor and reaffirm our commitment to advancing fundamental life science research and to further developing Japan’s first national infrastructure for laboratory mouse resources that support it.
RIKEN BioResource Research Center
Director, Toshihiko Shiroishi, Ph.D.