Japanese Immunologist Wins Nobel Prize for Groundbreaking Immune Cell Discovery
Professor Shimon Sakaguchi (right) receives a bouquet after the announcement of his Nobel Prize in Physiology or Medicine at Osaka University in Suita, Osaka Prefecture, on the afternoon of October 6. (©Sankei by Kotaro Hikono)
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On October 6, the Karolinska Institute in Sweden announced that the 2025 Nobel Prize in Physiology or Medicine will be awarded to three scientists. This includes Professor Shimon Sakaguchi, a distinguished professor at Osaka University.
Sakaguchi is being recognized for his groundbreaking discovery of regulatory T cells (Tregs) — a type of lymphocyte that suppresses excessive immune responses within the body.
His research transformed immunology and established new methods for treating autoimmune diseases, allergies, and cancer.
In 1995, Sakaguchi identified a molecule called CD25, which helped pinpoint a group of T cells that serve to restrain excessive immune responses.
The finding provided the first clear evidence of a cellular mechanism that prevents the immune system from attacking the body's own tissues.
In 2000, he named these cells "regulatory T cells." It was a discovery that has since become a cornerstone of modern immunology.
Japan's Nobel Prize success continues for the second consecutive year, following 2024's Peace Prize awarded to the Japan Confederation of Atomic and Hydrogen Bomb Sufferers Organizations (Nihon Hidankyo).
Sakaguchi's win marks the country's 30th Nobel Prize overall. It is also Japan's first in seven years in Physiology or Medicine. In 2018, Tasuku Honjo of Kyoto University was honored for his work on cancer immunotherapy.
Speaking to reporters outside his laboratory at Osaka University on Monday evening, Sakaguchi said, "I feel deeply honored." He expressed gratitude to his colleagues and students for their years of collaboration and support.
Sakaguchi will share the prize with Mary E Brunkow (Institute for Systems Biology, Seattle, USA) and Fred Ramsdell (Sonoma Biotherapeutics, San Francisco, USA).
The award ceremony will be held in Stockholm on December 10, where the three laureates will share a prize of 11 million Swedish kronor (about $1.17 million USD).
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Author: JAPAN Forward and The Sankei Shimbun
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