The 2025 Nobel Prize in Medicine has recognized three researchers in the field of immunology: Mary E. Brunkow and Fred Ramsdell from the United States and Shimon Sakaguchi from Japan, for their discoveries on peripheral immunological tolerance (1). This finding provides a fundamental understanding of how the immune system avoids attacking ourselves, thus preventing serious autoimmune diseases by moderating its aggression so as not to attack our own cells.

The work of Shimon Sakaguchi at Osaka University identified a subpopulation of T lymphocytes, called T regulatory cells (T-regs), characterized by the expression of the marker CD25 and the transcription factor FOXP3 (2). These cells act as a natural “brake” on the immune system, suppressing responses that could lead to autoimmunity or chronic inflammation.

For their part, Mary Brunkow and Fred Ramsdell identified the FOXP3 gene as a master regulator of T-reg function in murine models (Brunkow et al., Nature Immunology, 2001). Mutations in this gene cause IPEX syndrome (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked), a severe autoimmune disease in humans.

The identification of FOXP3 was a turning point that allowed us to connect genetics with immune regulation and opened the doors to a new therapeutic vision of autoimmune diseases. (1).

The Missing Piece: Regulatory T Cells

The immune system is designed to be a defense army against pathogens, however, a crucial challenge is to ensure that this army does not launch an attack against the body’s own cells and tissues.

The award-winning work focused on identifying and characterizing a specialized subtype of T lymphocytes, regulatory T cells, unlike other attacking T cells, act as a “natural brake” or “security guard” of the system, suppressing excessive immune responses and maintaining immune balance.

Scientific and Therapeutic Implications

The discovery of regulatory T cells and the FOXP3 gene has revolutionized modern immunology, changing the view that tolerance was only achieved by eliminating autoreactive cells in the thymus (central tolerance). The findings demonstrate that peripheral immunological tolerance is a dynamic and vital mechanism.

Relevance to the Diagnostic and Research Sector:

1. Autoimmune Diseases: Understanding this mechanism is essential for the development of new diagnostic biomarkers and therapies for conditions such as type 1 diabetes, lupus and rheumatoid arthritis, where the deregulation of these cells is a key factor.

2. Immunotherapy and Cancer: In oncology, inhibiting its function in the tumor microenvironment could free the immune system to attack cancer cells.

3. Organ Transplants:Controlled activation could reduce transplant rejection by suppressing the recipient’s immune response against the donated organ, decreasing the need for general immunosuppressants.

Currently, several therapies inspired by this tolerance mechanism are in clinical trials, underscoring the tangible impact of Brunkow, Ramsdell and Sakaguchi’s research on translational medicine and precision diagnosis (1).

Conclusion: the science of balance

The 2025 Nobel Prize highlights an essential principle of biology: life is not sustained only by defense, but by balance. The works of Brunkow, Ramsdell, and Sakaguchi reminded the world that the immune system, like society, needs boundaries that contain its own strength.

At In Vitro News, we celebrate this recognition as an example of how science can illuminate the finer self-regulation processes of life, and how basic research can be transformed into therapeutic hope.

References

1. Nobel Committee of the Karolinska Institute. The Nobel Prize in Physiology or Medicine 2025: Press Release. Stockholm: The Nobel Foundation; 2025 Oct 6.

2. Sakaguchi S, Sakaguchi N, Shimizu J, Yamazaki S, Waldmann H, Hori S, et al. Immunologic tolerance maintained by regulatory cells: their history and clinical perspectives. Immunol Rev. 2001;182(1):18-35.

3. Hori S, Nomura T, Sakaguchi S. Control of autoimmunity by naturally arising regulatory cells. Science. 2003;299(5608):1057-61.