Three scientists from the United States and Japan have won the 2025 Nobel Prize in Medicine for their groundbreaking work on how the immune system is regulated, paving the way for advances in treating autoimmune diseases, cancer, and improving transplant success.

The Nobel jury on Monday named Mary E. Brunkow and Fred Ramsdell of the US, alongside Shimon Sakaguchi of Japan, as this year’s laureates “for their discoveries concerning peripheral immune tolerance.”

Their findings transformed the understanding of immune function and why most people do not develop severe autoimmune conditions.

“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 jury said.

Sakaguchi, 74, made the first breakthrough in 1995, challenging the dominant belief that immune tolerance relied solely on the thymus eliminating harmful immune cells—a process known as central tolerance. He identified a previously unknown class of immune cells that play a critical role in protecting the body from autoimmune diseases.

In 2001, Brunkow, born in 1961, and Ramsdell, 64, made a second key discovery. They found that certain mice susceptible to autoimmune diseases carried a mutation in a gene they named Foxp3. They later showed that mutations in the human equivalent of Foxp3 cause a severe autoimmune disorder known as IPEX.

Two years later, Sakaguchi linked these findings, establishing a comprehensive understanding of how peripheral immune tolerance functions.

The trio will receive their prize — a diploma, a gold medal, and $1.2 million — from Sweden’s King Carl XVI Gustaf at a ceremony in Stockholm on December 10, the anniversary of Alfred Nobel’s death.

While US researchers continue to dominate the Nobel science categories, experts warn this could shift following major budget cuts to research programmes under President Donald Trump.

Since January, the US National Institutes of Health has terminated 2,100 research grants worth about $9.5 billion, as well as $2.6 billion in contracts, according to Grant Watch, an independent database.

Thomas Perlmann, secretary general of the Nobel Medicine Committee, told AFP that the US has been “the very engine” of global research.

“There would be very serious consequences for research globally if it starts to falter,” he said. “It doesn’t take very many years of large cutbacks to cause irreversible harm.”

Trump has repeatedly expressed his desire to win a Nobel Prize, particularly the Peace Prize, but experts say his “America First” stance and confrontational approach to global institutions make that unlikely.

“It’s completely unthinkable,” said Oeivind Stenersen, a historian and Nobel researcher. “(Trump) is in many ways the opposite of the ideals that the Nobel Prize represents.”

The Nobel announcements continue through the week, with physics on Tuesday, chemistry on Wednesday, literature on Thursday, peace on Friday, and economics on October 13.