The 2025 Nobel Prize in Physiology or Medicine has been awarded to three scientists for discovering why the immune system destroys infections but not the body’s own cells.
The prize is shared by Japan’s Shimon Sakaguchi and US researchers Mary Brunkow and Fred Ramsdell, who uncovered the existence of special immune cells known as regulatory T-cells — the body’s own “security guards” that prevent the immune system from turning against itself.
Their groundbreaking work transformed understanding of how the immune system functions and paved the way for new treatments for autoimmune diseases and cancer.
“Their discoveries have been decisive for our understanding of how the immune system functions and why we do not all develop serious autoimmune diseases,” said Olle Kämpe, chair of the Nobel Committee.
The trio share a prize fund worth 11 million Swedish kronor (€1m).
Regulatory T-cells travel through the body, disarming immune cells that mistakenly attack healthy tissue. When this process fails, autoimmune diseases such as type-1 diabetes, multiple sclerosis and rheumatoid arthritis can develop.
Their discovery also has major implications for cancer research — as these same cells can suppress the body’s ability to fight tumours. Researchers are exploring ways to either boost or reduce regulatory T-cells depending on the condition.
Prof Annette Dolphin, president of the UK’s Physiological Society, said: “This work is a striking example of how fundamental physiological research can have far-reaching implications for human health.”
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