Abstract
BACKGROUND: Kawasaki disease (KD), an acute vasculitis syndrome affecting children under 5 years, lacks specific biological markers for diagnosis. This study explores immune cell activation in KD patients during early vasculitis symptoms to identify potential diagnostic markers and guide intravenous immunoglobulin (IVIG) therapy timing. METHODS: The study included single-cell sequencing (SCS) from 10 patients, comprising seven with KD and three controls, as well as flow cytometry and polymerase chain reaction (PCR) validation from 277 patients. This included 95 children with KD and controls consisting of 12 healthy children and 170 children with febrile illnesses. Children with KD were divided into early vasculitis group and late vasculitis group based on whether the symptoms of vasculitis were less than or more than three days. peripheral blood mononuclear cells (PBMCs) were sequenced using the 10× Genomics platform, and flow cytometry and quantitative PCR (qPCR) verified changes in gene expression and cell proportions. RESULTS: KD patients showed higher CD19(+) B cells, particularly in the late vasculitis group. Pre-treatment CD19(+) B cells were elevated and normalized post-IVIG treatment. Flow cytometry validation confirmed the increase in CD19(+) B cells before IVIG treatment, which decreased to normal levels post-treatment, aligning with the SCS results. The study identified a total of 1,680 differentially expressed genes (DEGs) involved in B cell activation and immune responses, with core genes like IFITM1, CD55, FCER1G, and others down-regulated in the late vasculitis group. Time-series analysis revealed genes with high expression in early vasculitis that down-regulated over time, including S100A8, S100A9, and S100A12 which were further validated using qPCR, showing higher expression in the early stage of KD compared to healthy controls. CONCLUSIONS: This study highlights the close relationship between the number of immune cells and gene expression changes with the duration of vasculitis in KD, providing new insights into the pathophysiological mechanisms of the disease and potential prognostic indicators for clinical treatment.