Lymph nodes have long been considered simple “way stations” of the immune system — small filters where defensive cells are stored and trained before heading to the body’s battlefield. However, a new study published in Nature Immunology by a team from the University of Melbourne and the Doherty Institute has revealed something that could radically change the way we understand their role.
The study, led by Carlson Tsui and Axel Kallies, focused on understanding how T lymphocytes (the cells that identify and destroy infected or tumor cells) behave during persistent infection and under immunotherapy treatments. In particular, the researchers observed a special type of T cell called TPEX (precursors of exhausted T cells), which act as a kind of “stem reservoir” capable of self-renewal and generating new effector cells, even when the immune system is exhausted by prolonged exposure to antigens — as occurs in tumors or chronic infections.
These TPEX cells are fundamental for the success of immune checkpoint blockade (ICB) therapy, a treatment that releases the brakes of the immune system and allows T cells to regain their ability to attack tumors. What the study discovered is that these cells do not develop randomly within the body — their key “training zone” is the lymph nodes.
Using chronic infection models in mice, the researchers found that lymph nodes not only house a greater number of TPEX cells, but also maintain them in better functional condition than other organs, such as the spleen. The T cells within the lymph nodes showed greater proliferation (measured by Ki-67 expression), higher capacity to produce cytokines — molecules that coordinate the immune response — and a surprising resistance to exhaustion. Even when viral levels were high, lymphocytes within the nodes remained active, as if the microenvironment of these small organs granted them a competitive advantage. This was largely due to their interaction with migratory dendritic cells (cDC1), which bring antigens from peripheral tissues and present them to T cells, providing constant activation and survival signals.
KLF2: The Gene That Orchestrates the Fate of T Cells
One of the key aspects of the study was identifying which molecular mechanisms allow the lymph nodes to maintain this vital population of T cells. In this sense, the team discovered that the entire process depends on the transcription factor KLF2 (Krüppel-like factor 2), a protein that regulates the migration and development of T cells within lymphoid organs. T cells with high KLF2 expression not only migrated toward lymph nodes (thanks to receptors such as CCR7 and S1PR1), but also showed a remarkable ability to become TEX CX3CR1+ — “rejuvenated” T cells capable of regaining their effector power and circulating throughout the organism.
In contrast, when the researchers deleted the KLF2 gene using gene-editing techniques, these cells failed to form properly, disrupting the generation of new functional T cells. Instead, there was an increase in fully exhausted T cells (CD101+) with reduced ability to fight viruses or tumors. This finding demonstrates that KLF2 acts as a “conductor” that orchestrates the T cell life cycle, ensuring the immune army maintains a balance between regeneration and attack.
Figure 1. The diagram highlights the central contribution of lymph nodes as hubs that coordinate T cell regeneration and long-term immune competence. By integrating molecular signals and spatial organization, they enable continuous renewal of the antitumor T cell pool essential for effective and durable immunotherapy responses.
A Vital Migration Circuit for Immunotherapy
The study also showed that the movement of T cells between lymph nodes and the bloodstream is not a simple transit, but a carefully regulated process. When researchers blocked the CCR7 or S1PR1 receptor (which act like ID cards that allow entry into or exit from the lymph nodes), T cells stopped circulating properly, and the entire differentiation process became disorganized.
Lymph nodes thus act as central training and launching hubs: precursor T cells arrive, receive activation signals, proliferate, and then disperse throughout the body as effector cells ready to fight infections or tumors. Without this circuit, immunotherapy would lose part of its regenerative power, as there would not be enough “young” cells to respond to treatment.
This is why one of the most important messages emerging from this study — also highlighted by The Conversation — is that removing lymph nodes during cancer surgery could be counterproductive. Traditionally, many surgeons remove lymph nodes near the tumor to prevent metastasis or obtain a more accurate diagnosis. However, if these nodes are precisely where the most effective immune responses are generated, their removal could weaken the patient’s ability to respond to treatments such as PD-1 or PD-L1 blockade.
In fact, the authors suggest that lymph nodes should be considered allies of treatment, not just disease markers. Keeping them intact could enhance the effectiveness of immunotherapies and sustain the production of active T lymphocytes. In the future, physicians might even look for ways to “reactivate” lymph nodes or use targeted therapies on them to boost the immune response.
This work redefines how we understand the interaction between the lymphatic system and immunotherapy. Lymph nodes should no longer be seen as mere filters or diagnostic points but as strategic immune control centers where it is determined whether the body can sustain a prolonged response against cancer or, on the contrary, whether the system becomes exhausted.
Main reference:
Tsui, C., Heyden, L., Wen, L., Gago da Graça, C., Potemkin, N., Frolov, A., Rawlinson, D., Qin, L., Wimmer, V. C., Hadian-Jazi, M., Malko, D., Su, C. H., Li, S., Wilson, K. R., Horvatic, H., Wijesinghe, S. K., Moreira, M. L., Dryburgh, L., Schienstock, D., Rausch, L., … Kallies, A. (2025). Lymph nodes fuel KLF2-dependent effector CD8+ T cell differentiation during chronic infection and checkpoint blockade. Nature immunology, 26(10), 1752–1765. https://doi.org/10.1038/s41590-025-02276-7
Other references:
Baessler, A., & Vignali, D. A. A. (2024). T Cell Exhaustion. Annual review of immunology, 42(1), 179–206. https://doi.org/10.1146/annurev-immunol-090222-110914
McLane, L. M., Abdel-Hakeem, M. S., & Wherry, E. J. (2019). CD8 T Cell Exhaustion During Chronic Viral Infection and Cancer. Annual review of immunology, 37, 457–495. https://doi.org/10.1146/annurev-immunol-041015-055318
Blank, C. U., Haining, W. N., Held, W., Hogan, P. G., Kallies, A., Lugli, E., Lynn, R. C., Philip, M., Rao, A., Restifo, N. P., Schietinger, A., Schumacher, T. N., Schwartzberg, P. L., Sharpe, A. H., Speiser, D. E., Wherry, E. J., Youngblood, B. A., & Zehn, D. (2019). Defining ‘T cell exhaustion’. Nature reviews. Immunology, 19(11), 665–674. https://doi.org/10.1038/s41577-019-0221-9
