Cytokine profiles and clinical characteristics in primary Sjögren´s syndrome patient groups

Background Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by a lymphocytic infiltrate in salivary glands driving to epithelial damage. The pSS patients present heterogenic clinical and serological characteristics. This heterogenicity could be due to the cytokine microenvironment. Cytokine levels have been analyzed and reported individually, showing controversial results; for that reason, we considered essential to evaluate a cluster of cytokines and relate them with antibody levels and clinical characteristics to find pSS subgroups. Methods Ninety‐nine pSS patients, diagnosed by the 2016 ACR/EULAR classification criteria, and 76 control subjects (CS) were included. Cytokine quantification was performed by Multiplex assay. Principal component analysis (PCA) was realized, and the K‐mean test was used to identify clusters/groups. Groups were analyzed by the Kruskal‐Wallis test and the Bonferroni test. Results Higher IFN‐γ, IL‐17F, IL‐21, IL‐23, IL‐4, and IL‐31 levels were observed in pSS patients in comparison with control subjects. PCA analysis showed three groups. The severe group was characterized by higher cytokine concentrations as well as an increase in clinical parameters such as antibody levels, damage index score, and others. The moderate group presented intermediate severity; meanwhile, the mild group presented the lowest severity. Conclusion Cluster analysis revealed three groups that were different in cytokine levels and clinical parameters in which the mild group was defined by lower severity, the moderate group with intermediate severity, and the severe group with higher severity. This analysis could help subclassify the primary Sjögren syndrome patients for a better understanding of the clinical phenotype that impacts the treatment approach. Principal component analysis of 14 cytokines was realized to determine the cytokine groups in primary Sjögren´s syndrome patients. The mild group was characterized by less severity of the disease with low cytokine levels and fewer clinical parameters; the moderate group included patients with intermediate severity, presented higher cytokine levels than the mild group but less than severe group. Patients of the severe group showed higher severity, higher cytokine levels, and clinical parameters.