GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE294nnn/GSE294456/primaryOK200TranscriptomicsHomo sapiensExpression profiling by high throughput sequencinghttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE294456GEOGSEfalseSingle-cell TCR Profiling in Left Atria Identifies Complement Pathway Involvement in Atrial FibrillationAtrial fibrillation (AF) is the most prevalent arrhythmia and is strongly associated with stroke, heart failure, and increased mortality. However, the role of T cells in AF pathogenesis remains unclear. In this study, we aimed to characterize the detailed landscape and clonal expansion of T cells using single-cell TCR sequencing, and validate our findings via O-link proteomics in plasma. Analysis of left atrial tissues from eight AF patients identified five CD4+ T cells, six CD8+ T cells, and gamma delta T cells based on canonical gene expression markers. Notably, we observed clonal expansion of resident memory and cytotoxic T cells. CellChat analysis highlighted complement signaling–mediated interactions between T cells and fibroblasts. Furthermore, proteomics in plasma using the Olink platform confirmed enriched complement activation in non-paroxysmal AF compared to paroxysmal AF. These findings suggest that activation of complement pathway between T cells and fibroblasts contributes to atrial remodeling and may serve as a potential therapeutic target for AF.2026/04/01GSE294456GSM8906502GSM8906501GSM8906500GSM890649924676294456Homo sapiens