Cytokine Networks and Clinical Heterogeneity in Sjögren's Disease: From Glandular Inflammation to Therapeutic Stratification.

Sjögren's disease (SjD) is a chronic autoimmune disease characterized by lymphocytic infiltration and dysfunction of the exocrine glands, with manifestations extending beyond glandular sicca symptoms to multiple extraglandular systems. Although the pathogenesis of SjD remains incompletely understood, growing evidence indicates that a complex cytokine network involving both innate and adaptive immune pathways plays a central role in disease development. This narrative review summarizes recent updates on cytokine signaling in SjD across three clinically relevant domains. In glandular inflammation, activation of salivary gland epithelial cells through Toll-like receptor pathways triggers type I interferon (IFN) signaling via plasmacytoid dendritic cells, while IFN-γ, Th17-related cytokines (IL-6, IL-17, IL-22), BAFF/APRIL, and chemokines (CXCL10, CXCL12, CXCL13) collectively sustain local inflammation and ectopic lymphoid organization. The BAFF/APRIL axis, a systemic type I IFN signature, and IL-21-follicular helper T cell-B cell interactions primarily drive systemic immune activation, which together underlie autoantibody production, hypergammaglobulinemia, and a lymphoma-prone phenotype. In contrast, constitutional symptoms such as fatigue, pain, and dryness frequently dissociate from classical inflammatory activity and are better explained by neuroimmune-metabolic mechanisms, including the IFN-γ-IDO-kynurenine pathway and symptom-associated proteomic signatures. Collectively, these findings underscore the heterogeneous nature of SjD, in which glandular inflammation, systemic immune activation, and constitutional symptoms are driven by distinct yet partially overlapping cytokine pathways. Recognizing this heterogeneity has direct implications for cytokine-targeted therapy, suggesting that future trials should stratify patients by disease phenotype (IFN-high, B cell-dominant, and symptom-dominant) rather than treating SjD as a uniform population.