Medicine and Physiology Nobel 2025 For Discovery On How Immune System Is Kept Under Check

Scientists Mary Brunkow, Fred Ramsdell, and Shimon Sakaguchi have been awarded the 2025 Nobel Prize in Physiology or Medicine for their groundbreaking work on peripheral immune tolerance, the Nobel Committee announced. The trio identified regulatory T cells, often described as the immune system’s “security guards,” which prevent immune cells from attacking the body’s own tissues.

“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 Kämpe, chair of the Nobel Committee.

Shimon Sakaguchi made the first key discovery in 1995, challenging the prevailing belief that immune tolerance was solely established in the thymus through central tolerance. He revealed a previously unknown class of immune cells that protect the body from autoimmune diseases, showing that immune regulation is more complex than previously thought.

Mary Brunkow and Fred Ramsdell contributed a critical discovery in 2001, explaining why a particular mouse strain was highly susceptible to autoimmune diseases. They identified a mutation in the Foxp3 gene and demonstrated that mutations in the human equivalent cause a severe autoimmune disorder called IPEX.

Two years later, Sakaguchi linked these findings, showing that the Foxp3 gene controls the development of the regulatory T cells he had identified in 1995. These cells monitor other immune cells, ensuring that the immune system tolerates the body’s own tissues.

The laureates’ work has established the field of peripheral immune tolerance, paving the way for new treatments for cancer, autoimmune diseases, and improving outcomes in organ transplantation. Several therapies based on these discoveries are currently undergoing clinical trials.

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