T cells in Sjögren’s disease: update on their role in salivary gland pathogenesis and treatment

Sjögren's disease (SjD) is a chronic, systemic autoimmune disease that mainly targets saliva- and tear-producing glands. T-cells are a substantial immune cell subset involved in SjD pathogenesis, including break of tolerance toward self, and constitute a major part of tissue-resident and infiltrating immune cells in salivary glands (SGs) of patients with SjD. CD4⁺ T-cells provide help to B-cells, thereby contributing to B-cell hyperactivity in this disease. Yet, interactions between T-cells and non-immune cells, including epithelial cells and fibroblasts, and how such interactions contribute to the dysfunction of the glands are incompletely understood. Although CD4⁺ T helper cells have long been a major focus of research due to their dominance within inflammatory foci and their role in B-cell differentiation, growing evidence also implicates CD8⁺ T-cells in pathogenic processes within SG tissue. In this review, novel findings regarding the role of T-cells in SjD pathogenesis are discussed, focusing on their phenotype and function in SGs. Furthermore, treatments targeting T-cells directly or indirectly that have demonstrated clinical efficacy in SjD are reviewed. Studying the impact of these treatments on T-cells may shed new light on their role in SjD pathogenesis.