Background: Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease, which affects exocrine glands. T cell activation is a trigger mechanism in the immune response. Hyperreactivity of T cells and antibody production are features in pSS. ICOS can be critical in the pathogenesis of pSS. Methods: A total of 134 pSS patients and 134 control subjects (CS) were included. Genotyping was performed by PCR-RFLP. ICOS mRNA expression was quantified by real-time PCR, and CD4+ ICOS+ T cells were determined by flow cytometry. Results: The ICOS IVS1 + 173 T>C polymorphisms were not associated with susceptibility to pSS (p = 0.393, CI = 0.503–1.311). However, the c.1624 C>T polymorphism was associated with a reduction in the risk of development of pSS (p = 0.015, CI = 0.294–0.884). An increase in ICOS mRNA expression in patients was observed (3.7-fold). Furthermore, pSS patients showed an increase in membranal-ICOS expression (mICOS). High expression of mICOS (MFI) was associated with lymphocytic infiltration. Conclusions: The IVS1 + 173 polymorphism is not a genetic marker for the development of pSS, while c.1624 T allele was associated with a low risk. However, elevated mICOS expression in pSS patients with high lymphocytic infiltration was found. ICOS may have an important role in the immunopathogenesis of pSS and should be analyzed in T cell subsets in pSS patients as a possible disease marker.

Background/objectives: Sjögren’s disease (SjD) is an autoimmune disorder characterized by lymphocytic infiltration and inflammation leading to exocrine gland dysfunction. Th17 cells play a central role in autoimmune pathology and are defined by markers such as IL-23R, CCR6, and IL-17. However, the combined characterization of these markers and their relevance in SjD remain poorly understood. Methods: Forty-one participants were enrolled, including twenty-two patients with SjD and nineteen control subjects (CS). Peripheral blood immunophenotyping was performed using multicolor flow cytometry, and serum cytokine concentrations were quantified within a multiplex assay. Non-parametric analyses were conducted using the Mann–Whitney U test and Spearman’s rank correlation. Results: Compared with CS, patients with SjD exhibited higher frequencies of CD3⁺CD4⁺IL-23R⁺ T cells and elevated IL-23 levels. The proportion of CCR6⁺IL-23R⁺ T helper cells tended to be higher in SjD than in controls, although this difference did not reach statistical significance (8.8% vs. 5.3%, p = 0.056). Within clinical subgroups, anti-Ro-negative patients showed increased frequencies of CD3⁺CD4⁺IL-23R⁺ cells. Patients with hypertriglyceridemia displayed reduced frequencies of CCR6⁺IL-23R⁺IFN-γ⁺ cells, whereas normal HDL levels were associated with CCR6 expression and IL-17A production. Conclusions: These findings highlight the heterogeneity of Th17 cells in Sjögren’s disease and reinforce the involvement of the IL-23/IL-23R axis in disease pathogenesis. Exploratory associations between Th17 subsets and lipid parameters suggest a potential immunometabolic interplay that warrants further investigation. Together, these data provide a more comprehensive view of Th17 dynamics in SjD and establish a foundation for future mechanistic studies in larger cohorts and tissue-specific contexts.

Circulant follicular helper T cells (cTfh) are a specialized subset of CD4⁺ T cells that induce immunoglobulin class switching and antibody secretion in plasma cells through the production of IL-21. To investigate the role of cTfh-like cells in the development of Sjögren’s disease (SjD), we analyzed the circulating Tfh-like cells, their production of IL-21 and IL-4, and the co-expression of ICOS, CXCR5, and CCR9 by flow cytometry, and evaluated their association with clinical characteristics of the disease. Percentages of CD4⁺ IL-21⁺ CXCR5⁺ ICOS⁺ CCR9⁺ IL-4⁺ T cells were analyzed in peripheral blood samples from 20 healthy controls (HCs) and 19 patients with SjD. Serum levels of IL-1β, IL-4, IL-6, IL-21, and sCD40L were assessed using a Luminex assay. Laboratory data included anti-Ro/La antibodies, immunoglobulin levels (IgA and IgG), focus score, disease duration, and ESDDAI/SSDDI scores. Decreased frequencies of CXCR5⁺ IL-21⁺ T cells and CCR9⁺ IL-4⁺ T cells were observed in the peripheral blood of patients with SjD. Heatmap analysis was used to identify correlations between cTfh-like cells and clinical parameters. Elevated proportions of cTfh-like cells were positively correlated with disease severity, inflammatory markers, and autoantibody production. High-dimensional analysis identified distinct subpopulations with differential expression of ICOS, CXCR5, CCR9 and IL-21, suggesting heterogeneity of these cells in SjD and their involvement in disease pathogenesis.