Guardians Within: Scientists Win 2025 Nobel Prize for Revealing How the Immune System Protects the Body From Itself

A Discovery That Changed Immunology

The 2025 Nobel Prize in Medicine has been awarded to Shimon Sakaguchi of Osaka University, Japan, and Mary Brunkow and Fred Ramsdell from the United States. Their pioneering research revealed why our immune system built to destroy threats doesn’t turn its weapons against our own tissues.

Together, they identified a unique class of white blood cells known as regulatory T-cells (Tregs). Acting as the body’s internal “security guards,” these cells patrol the bloodstream, preventing rogue immune responses that could trigger devastating autoimmune diseases.

The trio’s discovery explained a mystery that has long puzzled scientists: how can an immune system powerful enough to fight off millions of infections also spare the body it defends?

“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.

Why It Matters

The immune system is a masterpiece of precision and adaptability. It creates white blood cells equipped with billions of unique receptors that can identify foreign invaders. But this randomness has a price some of these cells inevitably recognize and attack the body’s own tissues.

Until the 1990s, scientists knew that some self-reactive cells were destroyed in the thymus, where immune cells mature. Sakaguchi’s experiments in mice which developed autoimmune disease after having their thymus removed revealed something deeper. When he transferred certain immune cells from healthy mice, the disease stopped.

Those protective cells turned out to be regulatory T-cells, a crucial balancing force in immune tolerance.

Brunkow and Ramsdell later discovered the gene responsible for the development of these T-cells, confirming their central role in maintaining immune balance. Their genetic insights opened a new field of immunoregulation research, with vast clinical potential.

From Autoimmunity to Cancer: Two Sides of the Same Coin

In autoimmune diseases like type 1 diabetes, multiple sclerosis, and rheumatoid arthritis, the body’s immune system mistakenly attacks itself. Therapies are now being developed to boost regulatory T-cells, helping restore harmony.

In contrast, cancer uses these same regulatory cells to hide from the immune system. Some tumors attract Tregs to suppress the body’s natural defenses. Researchers are exploring ways to reduce or reprogram these cells so the immune system can once again recognize and destroy cancerous tissue.

Even organ transplant medicine may benefit enhancing T-cells could reduce rejection risks and promote long-term acceptance of new organs.

A Global Collaboration in Science

The 2025 Nobel story spans continents.

• Shimon Sakaguchi’s experiments at Osaka University built the biological foundation.

• Mary Brunkow at the Institute for Systems Biology in Seattle and Fred Ramsdell at Sonoma Biotherapeutics in San Francisco connected the genetics that made it all possible.

Together, their work shows how fundamental physiology research can yield life-changing medical applications.

Professor Annette Dolphin, president of the UK’s Physiological Society, praised the discovery as “a striking example of how fundamental research can have far-reaching implications for human health.”

A Decade of Discovery: Nobel Prize in Medicine 2015–2025

(Based on data from TVC News)

Each year’s breakthrough has deepened humanity’s understanding of life itself from the tiniest molecules to the grand orchestration of the immune system.

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