Redistribution of peripheral blood immune cell subsets and remodeling of intercellular communication in rare Behçet's disease: a single-cell transcriptomics study.

Background: Behçet's disease (BD) is a rare chronic systemic vasculitis of unknown etiology. The heterogeneity of peripheral blood immune cells and the dysregulation of intercellular communication in BD remain insufficiently characterized. The present study employs single-cell transcriptomics to comprehensively delineate the peripheral blood immune cell atlas of BD, identify candidate diagnostic biomarkers, and dissect the remodeling patterns of intercellular communication networks. Methods: Single-cell RNA sequencing data of peripheral blood mononuclear cells (PBMCs) from 8 BD patients and 8 healthy controls (HCs) (GSE198616) were analyzed using Seurat v5, clusterProfiler, LASSO regression, and CellChat v1.6. Differential expression analysis at both single-cell and pseudobulk levels, GSEA, and ssGSEA were performed, with external validation carried out using two independent transcriptomic datasets (GSE61399 and GSE205867). Results: Nine major immune cell types were identified, and monocytes were further subdivided into three subsets. BD patients exhibited subset-specific monocyte redistribution at the group level: CD14 Conclusion: This study delineates the peripheral blood immune landscape of BD, revealing subset-specific monocyte redistribution and subtype-specific remodeling of intercellular communication. These findings generate new hypotheses for diagnostic biomarker development and communication-targeted therapeutic strategies in BD, warranting further experimental validation in well-phenotyped cohorts.