3 scientists win Nobel Prize for breakthrough in immune system

American scientists Mary Brunkow and Fred Ramsdell and Shimon Sakaguchi from Japan won the 2025 Nobel Prize in Physiology or Medicine on Monday for work shedding light on how the immune system spares healthy cells, creating openings for possible new autoimmune disease and cancer treatments.

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The work by Mary Brunkow, Fred Ramsdell and Dr Shimon Sakaguchi uncovered a key pathway the body uses to keep the immune system in check, called peripheral immune tolerance. Experts called the findings critical to understanding autoimmune diseases such as Type | diabetes, rheumatoid arthritis and lupus.

Their discoveries relate to peripheral immune tolerance, or “how we keep our immune system under control so we can fight all imaginable microbes and still avoid autoimmune disease,” said Marie Wahren-Herlenius, a rheumatology professor at Sweden's Karolinska Institute, the awarding body.

The institute said all three laureates brought to the fore so-called regulatory T cells, a class of white blood cells that act as the immune system’s security guards that keep immune cells from attacking our own body.

Brunkow, who found out she had won after being woken by her dog barking at a news photographer on the front porch of her Seattle home, said she, Ramsdell and their colleagues had isolated a gene called FOXP3 that could be used as a marker for the cells.