The 2025 Nobel Prize in Medicine has been awarded to Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi for their discovery of the cellular and genetic mechanisms that maintain the balance of the immune system, preventing it from attacking the body’s own tissues.
Their work revealed how regulatory T cells (Tregs)—a minority of lymphocytes that act as immunological “brakes”—function, and how the FOXP3 gene is essential for their development and function. When this gene malfunctions, the body’s defenses spiral out of control, leading to severe autoimmune diseases such as IPEX syndrome, type 1 diabetes, or multiple sclerosis.
These findings explain the phenomenon known as peripheral immune tolerance—the body’s ability to distinguish between “self” and “non-self” in tissues where mature lymphocytes circulate. Without this mechanism, autoimmunity would be inevitable.
The clinical impact is profound: thanks to this knowledge, new strategies are being developed to prevent transplant rejection, modulate autoimmune responses, and, paradoxically, enhance anti-cancer immunity by temporarily inhibiting Tregs within the tumor microenvironment.
In summary, this Nobel Prize honors the discovery of the molecular guardians of tolerance, a breakthrough that redefines our understanding of the immune system and paves the way for more precise and safer therapies in immunology, transplantation, and oncology.
