In a groundbreaking discovery poised to reshape our understanding of immune function during chronic diseases, researchers at Memorial Sloan Kettering Cancer Center (MSK) and Weill Cornell Medicine have uncovered the pivotal role of a rare subset of T cells in sustaining the immune response. These cells, termed stem T cells, are now identified as the essential progenitors responsible for the continuous generation and replenishment of killer T cells, the immune system’s elite soldiers tasked with targeting infected or malignant cells. Central to the stemness and persistence of these cells is a protein called LEF1, which the scientists found to be a master regulator across disparate chronic conditions.
The immune system’s T cells are critical in the fight against infections and tumors, deploying targeted cytotoxic attacks. However, in prolonged battles such as chronic viral infections and autoimmune diseases, T cells progressively lose their efficacy, a phenomenon known as “T cell exhaustion.” Until now, the underlying cellular mechanisms enabling sustained T cell production during these chronic stresses remained elusive. The current study illuminates that the LEF1-expressing stem T cell subset not only acts as a reservoir but actively sustains immune vigour by giving rise to new effector T cells.
By employing advanced gene editing techniques, particularly CRISPR-Cas9, the researchers generated models in which LEF1 was specifically ablated from these scarce stem T cells. The effects were dramatic: without LEF1, these cells failed to self-renew and maintain their population, leading to a collapse in the T cell supply chain. Intriguingly, in a mouse model of type 1 diabetes, an autoimmune condition characterized by destructive immune attack on pancreatic beta cells, the absence of LEF1 conferred significant protection. This suggests that disabling the stem T cell compartment could mitigate autoimmune tissue damage by depleting the pathogenic cell reservoir.
Conversely, the study also demonstrated that enhancing LEF1 expression bolstered the formation of stem T cells and curtailed terminal differentiation into exhausted cells, particularly in the context of chronic viral infection modeled by lymphocytic choriomeningitis virus (LCMV). This juxtaposition highlights the dual mechanistic potential of LEF1 modulation: suppressing deleterious immune activity in autoimmunity and stimulating a rejuvenated immune response during persistent infections. As lead senior author Andrea Schietinger, PhD, elaborates, tuning LEF1 activity could be therapeutically calibrated to the specific immune landscape of chronic diseases.
A particularly surprising revelation was that stem T cells from autoimmune diabetes and chronic viral infection, despite their pathological differences, share an almost identical molecular signature guided by LEF1. High-dimensional computational analyses revealed 117 genes regulated in a congruent manner across both disease contexts, underscoring a conserved biological program orchestrating T cell stemness. This transcriptional unity challenges the notion that immune exhaustion and autoimmunity are fundamentally divergent at the stem cell level and instead proposes a universal stemness mechanism that sustains T cell populations under chronic physiological stress.
Further molecular dissection uncovered that the genetic pathways active in these stem T cells mirror those found in embryonic and adult stem cells residing in tissues like bone marrow and gut epithelium. This evolutionary parallelism implies that the immune system leverages a deeply conserved stem cell machinery to maintain T cell homeostasis, effectively co-opting stem cell niches and signaling networks traditionally associated with tissue renewal.
The “where” of stem T cells proved as vital as the “what.” Just like tissue stem cells, these immune progenitors depend on specialized microenvironments or niches that provide essential cues for self-renewal and survival. The team found that integrins and Notch signaling pathways are critical mediators of the localization and maintenance of stem T cells within lymph nodes and other immune compartments. Disrupting these signals precipitated the collapse of the stem T cell population, confirming that niche interactions are indispensable for sustaining immune longevity.
The translational implications are profound. The findings lay foundational knowledge for novel immunotherapies aimed at manipulating stem T cell reservoirs. In autoimmunity, therapies could target LEF1-positive stem T cells to extinguish pathogenic immune clones, thereby halting tissue destruction. In chronic infections and cancer, conversely, expanding this stem cell pool to prevent immune exhaustion could reinvigorate anti-pathogen and anti-tumor responses. This research opens a rational, mechanism-based avenue for precision immune modulation, a crucial step toward durable treatment responses.
This multidisciplinary investigation combines sophisticated genetic models, cutting-edge CRISPR editing, single-cell genomic profiling, and computational biology, exemplifying how complex biological questions can be dissected through collaborative innovation. The integration of computational analyses by co-corresponding author Doron Betel’s lab was key in defining the conserved LEF1-driven gene network, enriching the study’s conceptual depth.
Moreover, this work dovetails with the broader Marie-Josée and Henry R. Kravis Cancer Ecosystems Project at MSK, which views cancer through the lens of dynamic interactions between tumor cells and their microenvironment, including immune components. Understanding how stem T cells maintain themselves and communicate within their niches is central to this ecosystem approach, especially in engineering the microenvironment to foster cancer-fighting T cells.
Dr. Schietinger emphasizes that the next frontier is translating these fundamental insights into therapies that reprogram immune stemness to overcome cancer’s chronic immune challenges. Cancer’s classification as a chronic disease marked by progressive T cell dysfunction frames this research as pivotal to developing next-generation immune interventions.
In sum, the discovery that LEF1-dependent stem T cells govern immune resilience across seemingly disparate chronic diseases represents a paradigm shift in immunology. By unveiling a shared biological blueprint for sustaining immune progenitors, this work paves the way for innovative treatments that recalibrate immune homeostasis, with transformative potential for millions suffering from viral infections, autoimmune conditions, and cancer.
Subject of Research: Role of LEF1-positive stem T cells in maintaining immune function in chronic diseases including viral infections, autoimmune diabetes, and cancer.
Article Title: LEF1 and niche factors determine T cell stemness across chronic diseases
News Publication Date: July 1, 2026
Web References:
Cell Journal Article
DOI:10.1016/j.cell.2026.06.022
Image Credits: Memorial Sloan Kettering Cancer Center
Keywords: Stem cells, Autoimmune disorders, Viral infections, Immunology, Cancer research
Tags: autoimmune disease T cell functionchronic viral infection immune dynamicsgene editing in T cell researchimmune system persistence and LEF1immune system regeneration with stem T cellsLEF1 protein role in immune regulationnovel immunotherapy targets for chronic diseasesrare stem T cells in chronic diseasesstem T cells as progenitors of killer T cellssustained immune response in chronic infectionsT cell exhaustion mechanismsT cell stemness and chronic illness treatment
