Non-tuberculous mycobacteria, often abbreviated NTM, are environmental organisms that increasingly cause chronic and debilitating lung disease worldwide. Among them, Mycobacterium abscessus stands out as particularly menacing. It is naturally resistant to many standard antibiotics, it can form ropelike cords that shield it from engulfment by immune cells, and it thrives in patients with pre-existing lung damage such as bronchiectasis, cystic fibrosis, or pulmonary fibrosis. Treatment regimens typically stretch for many months, involve multiple toxic drugs, and frequently fail to eradicate the infection. Against this grim clinical backdrop, the question of how the immune system naturally fights M. abscessus has remained surprisingly underexplored, particularly with respect to γδ T cells, an unconventional lymphocyte population whose role in NTM infection had never been systematically characterized.

γδ T cells differ from the conventional αβ T cells that dominate textbook immunology. Rather than recognizing peptide fragments presented by major histocompatibility molecules, they respond rapidly to a wide range of stress signals and microbial products, earning them a reputation as a bridge between innate and adaptive immunity. A major subset of these cells produces interleukin-17A, a powerful inflammatory cytokine best known for recruiting neutrophils and shaping defenses at body surfaces. To determine whether these cells matter in M. abscessus infection, the researchers built a mouse model of pulmonary infection and mapped the immune landscape of lung tissue over the early days of disease using single-cell RNA sequencing, a technique that captures the gene expression profile of thousands of individual cells simultaneously.

The single-cell atlas revealed a striking pattern. As infection took hold, γδ T cells accumulated in the lung and expanded a population that expressed high levels of IL-17A. When the team removed γδ T cells entirely, using mice genetically engineered to lack them, the consequences were dramatic: bacteria persisted at far higher levels in the lungs and spleens, and lung inflammation worsened. Conversely, when γδ T cells were depleted in animals that had already cleared a first infection and were then re-challenged, the protective advantage of prior exposure evaporated. These experiments established γδ T cells as indispensable players in the early defense against M. abscessus, a finding that had not been demonstrated before for any non-tuberculous mycobacterial pathogen.

Delving deeper, the investigators identified IL-17A itself as the linchpin of this protective response. Mice unable to produce IL-17A lost much of their capacity to control the infection, and importantly, the defect traced back to the γδ T cells themselves. Without IL-17A signaling, the cells became less adept at recognizing the bacterium and lost much of their cytotoxic firepower. In an elegant series of transfer experiments, IL-17A-deficient γδ T cells failed to protect infected animals, whereas their normal counterparts succeeded. This revealed something unusual: IL-17A was not merely acting as a broadcast signal to other immune players but was required within the γδ T cells themselves, a cell-intrinsic requirement that underscores how tightly the cytokine and its producer are wired together during this infection.

The mechanism by which these cells actually kill the bacterium proved to be equally instructive. M. abscessus is an extracellular pathogen during key phases of infection, residing outside host cells in the airways and tissue spaces. The researchers found that IL-17A-positive γδ T cells eliminated extracellular bacteria through a granzyme B-dependent cytotoxic pathway. Granzyme B is a serine protease classically associated with the destruction of virus-infected or malignant cells, delivered through pore-forming perforin or other release mechanisms. Its deployment against free-living bacteria adds a new dimension to the antimicrobial portfolio of γδ T cells and explains how a lymphocyte population usually discussed in the context of autoimmunity and inflammation can act as a direct bactericidal weapon.

How, then, does the immune system know to mobilize these cells in the first place? The answer lies in a cascade that begins with Toll-like receptor 2, a pattern-recognition receptor on macrophages that detects components of the bacterial cell wall. When M. abscessus engaged TLR2 on lung macrophages, the macrophages responded by secreting two cytokines, interleukin-1β and interleukin-23. This cytokine pair is a well-known stimulus for IL-17 production in T cells, and in this context it drove both the expansion and the activation of the IL-17A-positive γδ T cell population. Blocking either IL-1β or IL-23 in infected mice diminished the γδ T cell response and impaired bacterial control, mapping out a complete signaling axis that runs from bacterial recognition through macrophage activation to lymphocyte mobilization and, ultimately, bacterial killing.

Perhaps the most clinically resonant aspect of the study concerns patients whose immunity depends on interferon-gamma, the canonical cytokine for defense against mycobacteria. A subset of individuals, particularly in Southeast Asia, develops autoantibodies that neutralize their own interferon-gamma, leaving them exquisitely vulnerable to disseminated NTM infections. Using single-cell RNA sequencing of peripheral blood cells from NTM patients, the researchers found evidence that anti-interferon-gamma autoantibodies compromise γδ T cell function in humans, mirroring what they observed in mice lacking the interferon-gamma receptor. Crucially, in mice engineered without functional interferon-gamma signaling, IL-17A-positive γδ T cells still conferred protection, and the same held true in a model combining M. abscessus infection with bleomycin-induced pulmonary fibrosis. In other words, this arm of immunity operates independently of the interferon-gamma axis and remains effective even in scarred, damaged lungs.

The implications for therapy are considerable. Current treatment of NTM disease relies almost entirely on antibiotics that the pathogen is adept at resisting, and there are no licensed immunotherapies that bolster host defenses. If the pathways defined in this study can be harnessed in patients, whether by stimulating IL-1β and IL-23 signaling, expanding protective γδ T cell populations, or delivering IL-17A-driven cytotoxic activity directly, clinicians could gain a means of strengthening the lung’s own antimicrobial machinery. Such approaches would be especially valuable for the growing population of patients with anti-interferon-gamma autoantibodies or structural lung disease, for whom conventional regimens offer diminishing returns. The researchers caution that translating mouse findings to the clinic will require careful work, particularly because IL-17A is also implicated in inflammatory conditions such as psoriasis and could carry safety risks if induced systemically. Nevertheless, the identification of a concrete, mechanistically defined cell type that can clear M. abscessus marks a genuine advance. It transforms γδ T cells from immunological bystanders into a promising therapeutic target, and it reframes the fight against antibiotic-resistant mycobacteria as a battle that the immune system, with the right encouragement, may be able to win on its own terms.

Subject of Research: The role of IL-17A-producing γδ T cells in controlling pulmonary Mycobacterium abscessus infection in mice.

Article Title: IL-17A-producing γδ T cells control pulmonary Mycobacterium abscessus infection in mice

Article References: Hu, X., Lin, S., Meng, W., Liu, H., Qin, Z., Wu, Z., Wan, Y., Ma, S., Yang, X., Yin, Z., Chu, Y., Zhang, W., Shao, L., & Lin, Y. (2026). IL-17A-producing γδ T cells control pulmonary Mycobacterium abscessus infection in mice. Nature Microbiology. https://doi.org/10.1038/s41564-026-02466-5

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DOI: 10.1038/s41564-026-02466-5

Keywords: Mycobacterium abscessus, non-tuberculous mycobacteria, γδ T cells, IL-17A, interferon-gamma, granzyme B, TLR2, IL-1β, IL-23, pulmonary infection, immunology, antibiotic resistance

Pulmonary fibrosis is a progressive disorder marked by the irreversible accumulation of extracellular matrix components, leading to diminished lung function and ultimately respiratory failure. Despite extensive research, effective treatments have remained elusive, partially due to the complex interplay of cellular and molecular players that orchestrate fibrotic processes. The researchers focused their attention on a subset of epithelial cells lining the lung alveoli, which have increasingly been recognized as active participants in disease pathogenesis rather than mere bystanders.

Central to the study is the transcriptional co-activator known as Yes-associated protein (YAP), which operates as a critical sensor of mechanical cues within the cellular microenvironment. YAP interacts with TEA domain transcription factors (TEADs) to regulate gene expression programs that govern cell proliferation, survival, and extracellular matrix production. The team hypothesized that aberrant activation of YAP-TEAD signaling in epithelial cells could be a driving force behind the fibrotic cascade.

Intriguingly, the study demonstrates that heightened YAP-TEAD activity induces the expression of lysyl oxidase (LOX), an enzyme responsible for cross-linking collagen fibers, thereby increasing tissue stiffness. The stiffened extracellular matrix further activates mechanotransduction pathways, resulting in a vicious cycle that exacerbates fibrosis. By establishing a direct link between epithelial YAP-TEAD signaling and LOX-mediated matrix remodeling, the authors provide a mechanistic framework that explains how epithelial cells contribute to pathological fibrosis.

To dissect the pathological significance of this signaling axis, the researchers employed a series of sophisticated preclinical models, including genetically engineered mice with conditional inactivation of YAP-TEAD components specifically in epithelial cells. These models revealed that deleting or pharmacologically inhibiting YAP-TEAD reduces LOX expression, attenuates collagen cross-linking, and markedly diminishes the extent of pulmonary fibrosis following lung injury. These findings underscore the therapeutic potential of targeting the epithelial YAP-TEAD/LOX pathway to halt or reverse fibrotic progression.

The team further augmented their analysis with single-cell RNA sequencing and spatial transcriptomics, techniques that allowed them to map cellular populations and gene expression patterns with unprecedented resolution. Their data pinpoint epithelial cells as the predominant source of YAP-driven LOX expression in fibrotic lungs, distinguishing them from mesenchymal cells, which have classically been viewed as primary ECM producers. This revelation challenges existing paradigms and expands the scope of potential cellular targets.

Another profound insight emerging from the study pertains to the regulatory feedback loops governing matrix stiffness and YAP activation. As extracellular matrix rigidity increases, YAP translocates to the nucleus more robustly, amplifying TEAD-mediated transcription. This biophysical interplay suggests that therapeutic interventions disrupting LOX activity or modifying matrix properties could indirectly mitigate YAP signaling, offering a multifaceted approach to functional restoration.

Importantly, the study also explored small-molecule inhibitors that disrupt YAP-TEAD interaction, such as verteporfin, demonstrating their efficacy in reducing fibrotic severity in vivo. These pharmacological agents recurrently suppressed LOX levels and collagen deposition, reinforcing the translational potential of targeting the YAP-TEAD interface. While verteporfin’s clinical applications have traditionally focused on ophthalmology, repurposing such compounds for fibrotic lung disease represents a compelling strategy.

In addition to experimental models, the researchers validated their findings in human lung tissue samples from patients with idiopathic pulmonary fibrosis (IPF). These analyses revealed strikingly elevated levels of YAP, TEAD targets, and LOX in diseased epithelia compared to healthy controls, confirming the clinical relevance of the molecular axis identified. By bridging animal and human data, the study solidifies a foundation for future clinical trials.

Delving deeper into the cellular microenvironment, the researchers uncovered that crosstalk between epithelial cells and fibroblasts is modulated by the YAP-TEAD/LOX pathway. Elevated LOX secretion alters fibroblast activation states, inducing a profibrotic phenotype characterized by enhanced matrix synthesis and contractility. This intercellular communication contributes to the relentless progression of fibrosis and highlights the complexity of cell-cell interactions orchestrating disease.

Mechanistically, the study illuminates how mechanical forces and biochemical signals converge in epithelial cells to maintain a pro-fibrotic niche. Integrin-mediated adhesion and cytoskeletal tension regulate YAP localization, while extracellular factors such as TGF-β potentiate transcriptional outputs. These layers of regulation underscore the adaptability of epithelial cells as central orchestrators of tissue remodeling, responding dynamically to their environment.

The trajectory of this research not only advances our understanding of pulmonary fibrosis but also heralds a paradigm shift in targeting epithelial signaling pathways. By focusing on the nucleus-centered relationship between YAP-TEAD and LOX, therapeutic approaches can be refined to intercept early pathogenic events rather than merely addressing downstream fibrosis.

Furthermore, the delineation of this pathway may have broader implications for other fibrotic diseases, including those affecting the liver, kidney, and heart, where epithelial or endothelial dysfunction plays a contributory role. The conservation of YAP-TEAD-mediated transcriptional programs hints at universal mechanisms of fibrosis, positioning this molecular axis as a nodal point for drug development.

As the scientific community eagerly anticipates translation of these findings, the authors advocate for further exploration into combinational therapies that integrate mechanical modulation, YAP-TEAD inhibition, and matrix-targeted treatments. Such multifactorial approaches may ultimately restore lung compliance and function, dramatically improving patient outcomes.

In summary, the discovery of the epithelial YAP-TEAD/LOX signaling pathway as a key driver of pulmonary fibrosis represents a landmark achievement, combining innovative molecular biology techniques with translational potential. It challenges longstanding dogma, redefines cellular contributors, and lays the groundwork for novel, targeted therapeutics aimed at one of the most vexing challenges in respiratory medicine.

Subject of Research: Pulmonary fibrosis and the molecular signaling pathways driving fibrosis in epithelial cells.

Article Title: Inhibition of epithelial cell YAP-TEAD/LOX signaling attenuates pulmonary fibrosis in preclinical models.

Article References:
Wagner, D.E., Alsafadi, H.N., Mitash, N. et al. Inhibition of epithelial cell YAP-TEAD/LOX signaling attenuates pulmonary fibrosis in preclinical models. Nat Commun 16, 7099 (2025). https://doi.org/10.1038/s41467-025-61795-x

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