10/18/2025
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The 2025 Nobel Prize in Medicine has been awarded to scientists who uncovered how the body prevents the immune system from attacking itself - a discovery that transformed our understanding of autoimmune disease and immune regulation. Y
our immune system is built to defend against viruses and bacteria, but if it isn’t properly restrained, that same power can turn inward, damaging your own organs. The mechanism that keeps this from happening is called peripheral immune tolerance, and it’s governed by a special group of cells known as regulatory T cells.
This year’s Nobel laureates, Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi, each played a key role in revealing how this system works. In 1995, Sakaguchi identified a previously unknown type of T cell that acted as a brake on immune responses, preventing self-destruction.
A few years later, Brunkow and Ramsdell discovered the gene that controlled these cells, known as FOXP3, while studying a rare and fatal autoimmune disorder in children. When this gene is mutated, the immune system loses control and begins attacking healthy tissue.
Sakaguchi later confirmed that FOXP3 was the master switch governing the regulatory T cells he had first described, completing the puzzle of how the immune system keeps itself in balance. Their discoveries explained the biological roots of autoimmune disease and also opened new paths in medicine.
Today, therapies based on regulatory T cells are being explored to treat autoimmune conditions, improve organ transplant outcomes, and even enhance cancer treatments by adjusting how the immune system responds around tumors.
