*

U.S. scientists Mary Brunkow and Fred Ramsdell, Japan's

Shimon

Sakaguchi win prize

Scientists' work relates to 'how we keep immune systems under

control'

*

Work spurred development of treatments in areas such as

cancer,

autoimmune disease

*

More than 200 trials on humans involving regulatory T

cells

under way

*

First award in 2025 Nobel Prizes, Physics next on Tuesday

(Recasts first paragraph, adds companies pursuing the approach

and potential treatment options in paragraphs 9-12)

By Johan Ahlander, Niklas Pollard and Ludwig Burger

STOCKHOLM, Oct 6 (Reuters) - 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.

This year's prize relates 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 the

Karolinska Institute.

Sakaguchi told reporters outside his university laboratory

that "I feel it is a tremendous honour," Kyodo news agency

reported.

REGULATORY T CELLS: THE IMMUNE SYSTEM'S 'SECURITY GUARDS'

The winners for medicine are selected by the Nobel Assembly

of Sweden's Karolinska Institute medical university and receive

a prize sum of 11 million Swedish crowns ($1.2 million), as well

as a gold medal presented by Sweden's king.

Brunkow is senior programme manager at the Institute for

Systems Biology in Seattle, while Ramsdell is scientific adviser

at Sonoma Biotherapeutics in San Francisco. Sakaguchi is a

professor at Osaka University in 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 in a statement.

The laureates identified so-called regulatory T cells, which

act as the immune system's security guards that keep immune

cells from attacking our own body, it added.

After announcing the winners, the institute's Thomas

Perlmann said specific therapies had yet to win market clearance

but more than 200 trials on humans involving regulatory T cells

were ongoing.

Among companies in the early race, Sonoma Biotherapeutics ,

which Ramsdell co-founded, is partly funded and supported by

U.S. drugmaker Regeneron to work on therapies against

diseases including inflammatory bowel disease.

Also targeting that condition, Quell Therapeutics has

partnered with AstraZeneca ( AZN ).

Other biotech firms exploring the approach include Bayer's

BlueRock.

MEDICINE THE FIRST PRIZE OF NOBEL SEASON

The Nobel Prizes were established through the will of Alfred

Nobel, the Swedish inventor of dynamite and a wealthy

businessman. They have been awarded since 1901 for outstanding

contributions in science, literature, and peace, with

interruptions mainly during the World Wars.

The economics prize was added later and is funded by

Sweden's central bank, the Riksbank.

Winners are selected by expert committees from various

institutions. All prizes are awarded in Stockholm, except for

the Peace Prize, which is presented in Oslo - a possible legacy

of the political union between Sweden and Norway during Nobel's

lifetime.

Past recipients of the Nobel Prize in Physiology or Medicine

include renowned scientists such as Alexander Fleming, who

shared the 1945 award for discovering penicillin. In recent

years, the prize has recognized major breakthroughs, including

those that enabled the development of COVID-19 vaccines.

Last year's medicine prize was awarded to U.S. scientists

Victor Ambros and Gary Ruvkun for their discovery of microRNA

and its key role in how multicellular organisms grow and live,

helping explain how cells specialise into different types.

Medicine in accordance with tradition kicks off the annual

Nobels, arguably the most prestigious prizes in science,

literature, peace and economics, with the remainder set to be

announced over the coming days.

More than a century after their inception, the Nobel Prizes

remain steeped in tradition. The awards culminate in ceremonies

attended by the royal families of Sweden and Norway, followed by

lavish banquets held on December 10 - the anniversary of Alfred

Nobel's death.

($1 = 9.3898 Swedish crowns)