Tissue‐Resident Memory CD8+ T Cells Acting as Mediators of Salivary Gland Damage in a Murine Model of Sjögren's Syndrome

Objective Although a role for CD4+ T cells in the pathogenesis of Sjögren's syndrome (SS) has been documented, the pathogenic significance of CD8+ T cells is unclear. The aim of this study was to investigate the role of CD8+ T cells in the development of SS. Methods Flow cytometry and immunofluorescence analyses were utilized to detect T cell infiltration within the labial salivary glands of patients with primary SS. In parallel, p40−/−CD25−/− mice were used as a murine model of SS. In addition, mice with genetic knockout of CD4, CD8a, or interferon‐γ (IFNγ) were crossed with p40−/−CD25−/− mice to study the pathogenic significance of specific lineage subpopulations, including functional salivary gland tests as well as histopathologic and serologic data. A CD8+ T cell–specific depletion antibody was used in this murine SS model to evaluate its potential as a therapeutic strategy. Results CD8+ T cells with a tissue‐resident memory phenotype outnumbered CD4+ T cells in the labial salivary glands of patients with SS, and were primarily colocalized with salivary duct epithelial cells and acinar cells. Furthermore, infiltrating CD8+ T cells with a CD69+CD103+/− tissue‐resident phenotype and with a significant elevation of IFNγ production were dominant in the submandibular glands of mice in this murine SS model. CD8a knockout abrogated the development of SS in these mice. Knockout of IFNγ decreased CD8+ T cell infiltration and gland destruction. More importantly, depletion of CD8+ T cells fully protected mice against the pathologic manifestations of SS, even after the onset of disease. Conclusion These data reveal the pathogenic significance of CD8+ T cells in the development and progression of SS in the salivary glands. Treatment directed against CD8+ T cells may be a rational therapy for the management of SS in human subjects.