Single-Cell RNA Sequencing Revealed the Role of Interferon-Gamma Related Genes in Primary Sjögren's Syndrome.

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder. Dysregulated interferon-gamma (IFN-γ) signalling is implicated in pSS pathogenesis, yet the underlying mechanisms remain elusive. This study aimed to identify key IFN-γ-associated diagnostic genes and delineate their roles in immune dysregulation using peripheral blood transcriptomic and single-cell RNA sequencing (scRNA-seq) data. Publicly available Gene Expression Omnibus (GEO) datasets were used, and the bioinformatics findings were further supported by reverse transcription-quantitative PCR (RT-qPCR) validation. Peripheral blood transcriptomic data from training and validation cohorts were analysed, and key genes were screened using machine learning algorithms, receiver operating characteristic (ROC) curve analysis, and differential expression analysis. A diagnostic model and nomogram were subsequently constructed. Immune infiltration, pathway enrichment, and gene regulatory networks were also investigated, while scRNA-seq analysis was performed to characterize cellular heterogeneity, pseudotime trajectories, and cell-cell communication. Four key genes, HERC6, IL15, CD58 and PTGS2, were identified, and the resulting diagnostic model and nomogram demonstrated high diagnostic accuracy. Immune profiling revealed marked dysregulation of the immune microenvironment in pSS, accompanied by extensive alterations in metabolic and signalling pathways. Pathway enrichment analysis further demonstrated both distinct and shared functional roles of the four key genes. Single-cell analysis suggested that macrophages may act as central regulators in pSS pathogenesis, as evidenced by altered pseudotime trajectories, enrichment in early differentiation states, and intensified cell-cell communication networks. RT-qPCR further confirmed the significant upregulation of HERC6, IL15, and PTGS2 in patients with pSS. Collectively, this study established an IFN-γ-associated diagnostic model for pSS and implicated macrophages as potential key contributors to immune dysregulation through altered differentiation, enhanced intercellular communication, and IFN-γ-associated gene expression. These findings provide new insights into the pathogenesis of pSS and identify potential diagnostic biomarkers and therapeutic targets.