Medicine Nobel for immune system researchers

The 2025 Nobel Prize in Physiology or Medicine has been awarded jointly to Mary E Brunkow and Fred Ramsdell of the US, and Shimon Sakaguchi of Japan for their discoveries concerning peripheral immune tolerance. The announcement was made on Monday by the Nobel Assembly at Karolinska Institutet.

The three scientists identified regulatory T cells, a class of immune cells that prevent the body’s immune system from attacking its own tissues. These cells act as monitors, ensuring that immune responses do not target the body itself.

“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 Kampe, chair of the Nobel Committee.

Sakaguchi first discovered a new type of immune cell in 1995 that helps prevent the body from attacking itself. At that time, scientists thought immune tolerance happened mainly through a process called central tolerance. Sakaguchi showed that another mechanism, called peripheral immune tolerance, also protects the body from autoimmune reactions.

In 2001, Brunkow and Ramsdell found that a gene called Foxp3 was linked to autoimmune diseases in certain mice. They also showed that mutations in the human version of this gene cause a serious autoimmune disorder.

Two years later, Sakaguchi proved that the Foxp3 gene controls the development of the immune cells he had discovered in 1995.

The cells, now known as regulatory T cells, maintain balance in the immune system by controlling other immune cells and preventing them from attacking the body’s own tissues.

Brunkow earned her doctorate from Princeton University and is a senior programme manager at the Institute for Systems Biology in Seattle. Ramsdell is a scientific adviser at Sonoma Biotherapeutics, while Sakaguchi is a distinguished professor at the Immunology Frontier Research Centre at Osaka University, Japan.

The 2025 Nobel Prize carries a cash award of 11 million Swedish kronor, equivalent to nearly Rs 103.87 crore. The Nobel Prize was established by Swedish inventor Alfred Nobel, who in his will directed that his estate be used to reward those who confer the greatest benefit to humankind.