Multidimensional single-cell analysis reveals immune dysfunction and inflammatory response in lymphatic malformations.

Lymphatic malformations (LMs) are debilitating and potentially life-threatening diseases. However, the immune phenotype of circulating cells and underlying molecular mechanisms in LMs remain poorly understood. Here, we performed integrated single-cell RNA, T-cell receptor, and B-cell receptor sequencing (scRNA-seq, scTCR-seq, and scBCR-seq) of peripheral blood and pleural effusion from patients with LMs to delineate their immune landscape. We identified an expansion of pro-inflammatory CD14+CD16+ monocytes and atypical memory B cells, accompanied by reduced cytotoxic CD8+ T and natural killer (NK) cells. Functional analysis revealed impaired antigen processing and presentation in CD14+ monocytes, and dysregulated transcription factor activity, potentially driving immune dysfunction. Additionally, LMs exhibited substantial remodeling of TCR and BCR repertoires, with shifts in clonality and diversity. Moreover, the CXCL16-CXCR6 interaction was associated with inflammatory responses, while upregulation of the inhibitory checkpoint HLA-E: CD94-NKG2A potentially contributed to impaired NK cell activity. Finally, we constructed a shared pro-inflammatory monocyte program and revealed S100A8 as a potential therapeutic target for LMs. We further demonstrated that S100A8 pharmacological inhibition could ameliorate the pathological phenotype of LMs. Collectively, our findings delineate cell type-specific immune dysregulation in LMs, offering insights for therapeutic development.