STOCKHOLM: American scientists Mary Brunkow and Fred Ramsdell, along with Shimon Sakaguchi of Japan, won the 2025 Nobel Prize in Physiology or Medicine on Monday for their discoveries in peripheral immune tolerance, opening doors for potential new treatments for autoimmune diseases and cancer.

“This year’s prize relates to how we keep our immune system under control so we can fight all imaginable microbes and still avoid autoimmune disease,” said Marie Wahren-Herlenius, rheumatology professor at the Karolinska Institute.

Sakaguchi told reporters outside his university laboratory, “I feel it is a tremendous honour,” according to Kyodo News Agency.

The laureates, selected by the Nobel Assembly at Karolinska Institute, receive 11 million Swedish crowns ($1.2 million) and a gold medal presented by Sweden’s king.

Brunkow is senior programme manager at the Institute for Systems Biology in Seattle, Ramsdell is scientific adviser and co-founder at Sonoma Biotherapeutics in San Francisco, and Sakaguchi is a professor at Osaka University, Japan.

“Their discoveries have laid the foundation for a new field of research and spurred the development of new treatments, for example for cancer and autoimmune diseases,” the prize-awarding body said. The trio identified regulatory T cells, immune system “security guards” that prevent the body from attacking itself.