The 2025 Nobel Prize in Physiology or Medicine has been awarded to Mary Brunkow, Fred Ramsdell and Shimon Sakaguchi for their groundbreaking discoveries related to regulatory T cells — the “security guards” of the immune system. These specialized cells prevent the body’s own immune defense from mistakenly attacking healthy tissues.
Their research has transformed scientific understanding of a vital immune mechanism known as peripheral tolerance. When regulatory T cells malfunction or are too few in number, the immune system can become overactive, leading to autoimmune disorders such as type 1 diabetes, rheumatoid arthritis and multiple sclerosis.
The laureates’ discoveries are now paving the way for innovative medical treatments. Scientists have found that tumors can recruit large numbers of regulatory T cells to shield themselves from immune attacks — a kind of cellular camouflage. To counter this, new cancer therapies are being tested to dismantle the protective barrier of regulatory T cells so the immune system can better target tumor cells.
Conversely, increasing regulatory T cells is emerging as a promising approach for autoimmune diseases and organ transplantation. Early-stage clinical trials are using interleukin-2 to help these immune-regulating cells thrive, with the goal of reducing harmful inflammation and preventing rejection of transplanted organs.
Another strategy being explored is cell therapy: isolating regulatory T cells from a patient, multiplying them in the lab, and returning them to the body to boost immune control. In some cases, the cells are engineered with antibodies like “address labels” so they travel directly to a specific organ — such as a transplanted kidney — to protect it from immune attack.
Experts say this is just the beginning of a new wave of immunotherapies built on regulatory T-cell science.
By revealing how the immune system keeps itself in balance, Brunkow, Ramsdell, and Sakaguchi have laid the foundation for treatments that could benefit millions worldwide — a contribution the Nobel Committee recognized as having “the greatest benefit to humankind.”
