Shimon Sakaguchi

is a Japanese immunologist. He is a distinguished professor at Osaka University and a professor emeritus at Kyoto University.

His work includes the discovery of regulatory T cells and describing their role in the immune system. In 2025, he was jointly awarded the Nobel Prize in Physiology or Medicine with Mary E. Brunkow and Fred Ramsdell.

Early life and education Shimon Sakaguchi was born on 19 January 1951 in Nagahama, Shiga. He received a medical degree in 1976 from the Faculty of Medicine at Kyoto University. In 1982, he also received a PhD degree from Kyoto University.

Career Sakaguchi undertook postdoctoral research in the United States at Johns Hopkins University and Stanford University from 1983 to 1987 as a Lucille P. Markey Scholar. Later, he worked as an assistant professor in the Department of Immunology at the Scripps Research Institute. Later, he became the head of the Department of Immunopathology at the Tokyo Metropolitan Institute of Gerontology. His lab was moved to Osaka University in 2011.

Research

In a 1995 study, Sakaguchi and his colleagues showed the existence of regulatory T cells, a previously unknown subset of T cells expressing CD4 and CD25 that modulate the immune system and help maintain immune tolerance. They injected BALB/c athymic mice with a suspension of CD4+ cells previously depleted of CD25+ cells and found that the mice subsequently developed autoimmune diseases (e.g. thyroiditis and gastritis). However, reconstitution of CD4+CD25+ cells shortly after the initial injection of CD4+CD25− cells prevented the development of autoimmunity. In 2003, Sakaguchi's group demonstrated the importance of FOXP3 in the development and function of regulatory T cells. 2008: Keio Medical Science Prize (with Fred Gage) 2009: Medal of Honor with Purple Ribbon (Japan) 2011: Asahi Prize 2012: Foreign associate of the National Academy of Sciences 2015: Chunichi Culture Award 2015: Canada Gairdner International Award 2015: Clarivate Citation laureates in Physiology or Medicine (with Shevach and Alexander Rudensky) 2017: Crafoord Prize (with Ramsdell and Rudensky) 2017: Person of Cultural Merit (Japan) 2017: 2019: Order of Culture (Japan) 2020: Paul Ehrlich and Ludwig Darmstaedter Prize 2020: Robert Koch Prize 2023: Debrecen Award for Molecular Medicine 2025: Nobel Prize in Physiology or Medicine (with Brunkow and Ramsdell)