A trio of US and Japanese scientists have been awarded the 2025 Nobel Prize in Physiology or Medicine for their discovery on how the immune system is kept in check.

The coveted prize by the Nobel Assembly at Karolinska Institutet was awarded to Mary E. Brunkow (US), Fred Ramsdell (US), and Shimon Sakaguchi (Japan). The prize money of 11 million Swedish kronor will be shared equally between the laureates.

“The 2025 #NobelPrize in Physiology or Medicine has been awarded to Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi for their discoveries concerning peripheral immune tolerance,” the Nobel Assembly said in a statement.

The peripheral immune tolerance is a mechanism that prevents the immune system from harming the body.

The laureates identified the immune system’s security guards,

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