The 2025 Nobel Prize in Medicine has been awarded to Mary E. Brunkow-USA, Fred Ramsdell-USA, and Shimon Sakaguchi-Japan, for their groundbreaking work on how the human immune system functions and maintains balance.

Announced by Sweden’s Karolinska Institute on Monday, the trio will receive the prize in December for their discoveries related to peripheral immune tolerance, a mechanism that prevents the immune system from attacking the body’s own cells.

“This research explains how our immune system stays controlled allowing us to fight infections while avoiding autoimmune diseases,” said Marie Wahren-Herlenius, a rheumatology professor at the Karolinska Institute.

The three laureates will share the 11 million Swedish kronor (about $1.17 million) prize equally. The King of Sweden will present them with the Nobel gold medals during the official ceremony.

According to the Nobel committee, their discoveries have opened new fields of medical research and inspired the development of treatments for cancer and autoimmune diseases.

The Medicine Prize marks the beginning of this year’s Nobel season, followed by awards in physics, chemistry, literature, peace, and economics in the coming days.