Peripheral Immune Tolerance: Discovery, the Path to the Nobel Prize, and Beyond
March 11, 2026
Distinguishing between self and nonself is fundamental to the immune system, enabling it to mount an appropriate response. While antigens (nonself) trigger an immune attack, the body must remain unresponsive to its own cells (self). This self‑tolerance is primarily established through central tolerance, in which potentially self‑reactive T lymphocytes are eliminated.¹ However, some T cells escape this process and can recognize and attack self molecules, leading to horror autotoxicus or autoimmunity.
How does the immune system prevent this outcome? How is peripheral self‑tolerance maintained? And what players form the regulatory network behind it? These questions inspired a small but determined group of scientists—and ultimately reshaped our understanding of immunology.
As researchers worldwide explored fundamental questions in immune regulation, the commitment of Waters Biosciences (formerly BD Biosciences) to advancing human health provided the critical tools that helped make these discoveries possible.
The Discovery of Peripheral Tolerance
In the 1990s, Japanese immunologist Shimon Sakaguchi investigated the regulatory components of the mouse immune system. Using 3‑color flow cytometry, he identified a critical population of T cells marked by the surface proteins CD4⁺ and CD25⁺, which he termed regulatory T cells (Tregs). These cells proved essential for maintaining self‑tolerance in mice. This phenomenon, now known as peripheral immune tolerance, revealed an additional layer of immune regulation functioning alongside central tolerance.
Around the same time in the United States, Mary Brunkow and Frederick Ramsdell identified the gene that controls Treg function. Through genetic mapping, mutation analysis, intracellular staining, and flow cytometry, they pinpointed FoxP3 as a key regulator of immune tolerance.² Their work on the “scurfy mouse” demonstrated that mutations in FoxP3 lead to a loss of tolerance, and that correcting these mutations restores normal immune function. They later identified the human equivalent of FoxP3 and linked it to the disorder IPEX.³ This discovery established a definitive role of FoxP3 in immune tolerance.
Further confirmation came from Sakaguchi’s 2003 work showing that FoxP3 is selectively expressed in CD4⁺CD25⁺ T cells and directs Treg development, cementing the CD4⁺CD25⁺FoxP3⁺ signature as the defining marker of Tregs.⁴
Collectively, these discoveries earned Sakaguchi, Brunkow, and Ramsdell the 2025 Nobel Prize in Physiology or Medicine.⁵
These Nobel Prize–winning discoveries were supported by the rapid evolution of flow cytometry technology and advancements that BD Biosciences has helped drive for over 50 years, enabling the foundational science behind today’s immunology breakthroughs.
Flow Cytometry Technology that Enabled the Discovery
Although scientists suspected the existence of additional regulatory immune mechanisms, the tools to identify them were previously inadequate. Advances in flow cytometry, particularly the development of 3‑color analysis and high‑quality monoclonal antibodies from BD Biosciences, made it possible to distinguish T‑cell subsets with specific surface markers. Techniques such as intracellular staining, high‑purity cell sorting, and sensitive detection were essential to isolating and characterizing Tregs.
Interest in regulatory T cells has surged as researchers explore their pivotal role in various frontiers such as cancer immunotherapy, autoimmune diseases, cell therapy development and understanding transplant tolerance.
How Waters Biosciences Is Transforming the Future of Treg Research
Since the initial discovery of regulatory T cells, flow cytometry has advanced dramatically. Breakthroughs in high‑parameter spectral flow cytometry have expanded analytical capabilities more than tenfold.
The BD FACSDiscover™ platform allows researchers to analyze 40–50+ parameters in a single experiment with sophisticated spectral unmixing. Instruments like the BD FACSDiscover™ A8 Cell Analyzer and the BD FACSDiscover™ S8 Cell Sorter combine spectral flow cytometry with cellular imaging and cell sorting, enabling unprecedented Treg interrogation. The BD FACSDiscover™ S8 Cell Sorter offers sort‑capable real-time imaging, allowing researchers to isolate Tregs based on morphology and phenotype simultaneously.
In addition, next‑generation fluorochromes with reduced spectral overlap facilitate the detection of dim markers such as CD25, significantly improving sensitivity and resolution. Collectively, these advancements empower researchers to probe Treg biology at depths previously thought impossible.
Using the Right Tools to Advance Immunology Research
Scientific progress depends on both discovery and technology. A deep understanding of available scientific tools enables researchers to push the boundaries of immunology.
To support next‑generation Treg research, we have developed an infographic highlighting the capabilities of our breakthrough technologies and their applications in immunology.
