Shimon Sakaguchi

Shimon Sakaguchi (born 19 January 1951) is a Japanese immunologist, a distinguished professor at Osaka University and professor emeritus at Kyoto University. Born in Nagahama, Shiga, he took his medical degree at Kyoto University in 1976 and a doctorate there in 1982, then did postdoctoral work at Johns Hopkins and Stanford. His research established the existence of regulatory T cells: in a 1995 study he and colleagues showed that a subset of CD4 T cells carrying CD25 restrains the immune system and prevents autoimmune disease in mice, and in 2003 his group showed the importance of the FOXP3 gene for these cells. For this work he shared the 2025 Nobel Prize in Physiology or Medicine with Mary Brunkow and Fred Ramsdell, for discoveries concerning peripheral immune tolerance. He has also received the Crafoord Prize and the Robert Koch Prize.