Interferon-Gamma Emerges as a Potential Hub Linking Inflammation to Fibrosis in Sjögren’s Lung Disease

Interstitial lung disease is the most feared complication of Sjögren’s disease, a chronic autoimmune disorder best known for destroying the salivary and lacrimal glands. Once lung involvement takes hold, quality of life collapses, mortality reaches 16 percent at five years, and the ten-year risk of death is quadrupled. Yet the molecular machinery driving this progression has remained frustratingly opaque. A new narrative review published in Immunity, Inflammation and Disease now assembles a pathway-level framework proposing that interferon-gamma, the signature cytokine of Th1 immune cells, may act not as a lone inflammatory messenger but as a regulatory node within an interconnected signaling web that connects systemic immune dysregulation to pulmonary inflammation and, ultimately, fibrotic remodeling.

The review’s authors systematically mapped six signaling pathways that may fall under interferon-gamma’s influence: JAK/STAT, PI3K/AKT, NF-κB, MAPK, WNT/β-catenin, and the IDO–kynurenine–AhR axis. Crucially, they graded the evidence behind each link, acknowledging that direct mechanistic data in Sjögren’s-associated interstitial lung disease remain scarce. The JAK/STAT pathway, through which interferon-gamma signals via JAK1 and JAK2 to phosphorylate STAT1, carries the strongest support. The intermediate pathways rest on extrapolation from related autoimmune and fibrotic lung diseases, while the WNT and IDO–kynurenine–AhR connections are explicitly labeled exploratory. This candor distinguishes the work from typical mechanistic reviews and provides a roadmap for what must be validated rather than a settled biological hierarchy.

The clinical stakes are considerable. Epidemiologic studies place the prevalence of interstitial lung disease in Sjögren’s patients at 3 to 11 percent, and the histopathological spectrum ranges from nonspecific interstitial pneumonia, the most common pattern, to usual interstitial pneumonia, which a large cohort of 558 patients recently linked to impaired pulmonary function and increased mortality. High-resolution computed tomography typically reveals ground-glass opacities, reticulation, and traction bronchiectasis, while pulmonary function tests show restrictive defects with a disproportionate drop in diffusing capacity. Within the lung, injury to alveolar epithelial type II cells impairs surfactant production and repair, while aberrantly activated fibroblasts deposit extracellular matrix and stiffen tissue, creating the structural context in which interferon-gamma-driven signaling could operate.

Interferon-gamma itself is a type II interferon, structurally distinct from the type I interferons that have long dominated Sjögren’s research. It circulates as a homodimer and engages a tetrameric receptor complex displayed on both immune and non-immune cells. Produced chiefly by activated CD4-positive Th1 cells, CD8-positive T cells, and natural killer cells, the cytokine activates macrophages, licenses dendritic cells by up-regulating MHC molecules and co-stimulatory markers, and steers naïve T cells toward a Th1 fate. It also primes production of tumor necrosis factor-alpha, interleukin-12, and interleukin-1β, and can synergize with toll-like receptor signals to create a self-reinforcing inflammatory loop. In Sjögren’s disease specifically, elevated circulating interferon-gamma has been associated with higher disease activity, and an elevated Th1-to-Th2 ratio correlates significantly with the presence of interstitial lung disease.

The review highlights several mechanisms that could amplify interferon-gamma output in patients. The rs2069705 polymorphism enhances STAT4 binding to the interferon-gamma promoter and increases susceptibility to Sjögren’s disease. Regulatory T cells, which normally restrain Th1 responses, are reduced in both peripheral blood and salivary glands, with the deficit inversely correlating with disease activity as measured by the ESSDAI index. Meanwhile, interferon-responsive chemokines CXCL9, CXCL10, and CXCL11 are sharply up-regulated in serum and salivary gland tissue, potentially recruiting additional CXCR3-expressing T cells into an expanding inflammatory circuit. Recent work also identifies interferon-gamma as a key effector driving salivary gland epithelial cell death and hypofunction, suggesting the cytokine’s pathogenic reach extends beyond immune cells to the structural tissue itself.

At the network level, the proposed model organizes these pathways into layers. Upstream, the interferon-gamma–JAK/STAT axis drives immune-cell activation and chemokine production. In the middle, PI3K/AKT, NF-κB, and MAPK function as amplification and regulatory modules. PI3K/AKT governs immunometabolic reprogramming and B-cell survival, a relevant point given that aberrant B-cell activation and autoantibody production are hallmarks of Sjögren’s pathology, and lupus studies have demonstrated interactions between interferon-gamma signals and PI3K-dependent B-cell responses. NF-κB integrates inflammatory signals and may sustain a pro-inflammatory macrophage state, while MAPK cascades coordinate stress and growth-factor inputs, with experimental evidence linking interferon-gamma-associated p38 and ERK activation to epithelial-to-mesenchymal transition, a pro-fibrotic cellular program.

Downstream, the WNT/β-catenin pathway emerges as the fibrotic executor. Chronic inflammation can switch WNT from a developmental signal into a pathological remodeling program: inflammatory cytokines such as tumor necrosis factor-alpha, interleukin-1β, and transforming growth factor-beta influence β-catenin stability, while inflammatory stress represses WNT antagonists, lifting the brakes on the pathway. Across chronic lung diseases, WNT/β-catenin activation correlates with fibroblast proliferation, myofibroblast differentiation, collagen deposition, and tissue stiffness. Altered WNT signaling has been documented in Sjögren’s salivary glands, though its role in the diseased lung remains poorly characterized. The more speculative IDO–kynurenine–AhR axis adds a metabolic layer: sustained interferon-gamma exposure induces indoleamine 2,3-dioxygenase in macrophages and dendritic cells, shunting tryptophan toward kynurenine, which activates the aryl hydrocarbon receptor and reshapes immune tolerance and immune–stromal interactions.

The therapeutic implications are among the most consequential aspects of the framework. Because the JAK/STAT axis carries the strongest evidence, JAK inhibitors such as tofacitinib, baricitinib, and upadacitinib represent the most immediate candidates for modulating interferon-gamma-driven inflammation, particularly in inflammation-dominant disease, although clinical benefit in Sjögren’s-associated interstitial lung disease has not been established. B-cell-directed therapies intersect with the same immune network; real-world data from a multicenter European cohort of 191 patients showed rituximab was used in 25.1 percent of cases, though observational data cannot establish efficacy. For patients who progress to a fibrotic phenotype, the antifibrotic nintedanib, which has demonstrated efficacy in progressive fibrosing interstitial lung diseases across diagnoses, offers a rationale for intervention even though it does not directly target interferon-gamma signaling. The extensive cross-talk among downstream pathways suggests, however, that single-pathway inhibition may prove insufficient for established fibrosis, pointing toward combinatorial, stage-specific strategies.

The authors are careful to frame their model as hypothesis-generating rather than validated. Much of the mechanistic scaffolding derives from associative data, experimental models, or extrapolation from idiopathic pulmonary fibrosis and other connective tissue disease-associated lung diseases. Disease heterogeneity, including variability in immune-cell composition, inflammatory burden, and genetic background, likely shapes which pathways dominate in individual patients. The proposed hierarchy of upstream, intermediate, and downstream modules is explicitly a theoretical synthesis. Prospective validation in longitudinal cohorts, ideally integrating spatial transcriptomics and single-cell profiling, will be required to confirm the temporal sequence and relative contribution of each pathway.

If that validation succeeds, the payoff could be substantial. Biomarkers such as serum CXCL9, CXCL10, KL-6, and even CA125, which a prospective multicenter cohort of 395 patients independently associated with adverse outcomes, could enable patient stratification and disease monitoring aligned with specific pathway activity. More broadly, the review exemplifies a conceptual shift in autoimmune lung disease research: away from linear cytokine cascades and toward multidimensional signaling networks in which immune activation, metabolic reprogramming, and fibrotic remodeling are coupled layers of a single pathogenic architecture. For a disease whose pulmonary complications quietly quadruple mortality risk, that systems-level perspective may finally offer a path toward precision medicine.

Subject of Research: Interferon-gamma-associated signaling networks in Sjögren's disease-associated interstitial lung disease

Article Title: IFN‐γ‐Associated Signaling Networks in Interstitial Lung Disease Associated With Sjögren's Disease

Article References: Chen, Q., Li, Y., Chen, Y., Su, Y., Wang, X., & Guan, C. (2026). IFN‐γ‐Associated Signaling Networks in Interstitial Lung Disease Associated With Sjögren's Disease. Immunity, Inflammation and Disease, 14(10), Article e70547. https://doi.org/10.1002/iid3.70547

Image Credits: AI Generated

DOI: 10.1002/iid3.70547

Keywords: Sjögren's disease, interstitial lung disease, interferon-gamma, JAK/STAT, pulmonary fibrosis, NF-κB, PI3K/AKT, MAPK, WNT/beta-catenin, CXCL10, JAK inhibitors, autoimmunity