Accumulating data implicate Type Ⅲ interferons (IFN-λs) in autoimmune disorders, prompting our exploration of their role in uveitis pathogenesis. Serum and peripheral blood mononuclear cells (PBMCs) from patients with active Vogt-Koyanagi-Harada (VKH) and active Behçet’s disease (BD) were analyzed for IFN-λ expression by enzyme-linked immunosorbent assay and real-time quantitative PCR. Experimental autoimmune uveitis (EAU) was induced in IFNLR1^−/− mice to evaluate disease severity, inflammatory responses, and blood-retinal barrier (BRB) integrity. RNA sequencing and bioinformatic analyses were performed to identify related genes and associated signaling pathways. IFN-λ levels were significantly elevated in active VKH and BD patients and effectively distinguished them from healthy controls. Compared with wild-type mice, IFNLR1^−/− mice developed more severe EAU, characterized by increased Th1/Th17 responses, reduced Treg frequency, and disrupted blood-retinal barrier integrity, which was evidenced by decreased tight junction proteins ZO-1, Claudin-5, and Occludin. Both retinal pigment epithelium (RPE) cells from IFNLR1^−/− mice and human primary retinal pigment epithelium (RPE) cells with silenced IFNLR1 secreted higher levels of interleukin (IL)-6, IL-8, IL-1β, and MCP-1, which were suppressed by recombinant IFN-λ1 and IFN-λ2. RNA sequencing revealed an enrichment of T-cell and NOD-like receptor signaling pathways in IFNLR1^−/− EAU mice. Consistent with this transcriptional profile, the expression of NLRP3 and NLRP1 was upregulated in RPE cells. Knockdown of these inflammasomes reduced proinflammatory cytokine production and upregulated the tight junction proteins. These results suggest that IFN-λs may alleviate uveitis by targeting RPE cells, primarily through downregulation of NLRP1/NLRP3 inflammasome activity, thereby attenuating inflammatory responses and preserving BRB integrity.

Vogt-Koyanagi-Harada disease (VKH) is a rare autoimmune disease characterized by diffuse and bilateral uveitis, alopecia, tinnitus, hearing loss, vitiligo and headache. The transcriptional expression pattern of peripheral blood mononuclear cells (PBMC) in VKH remains largely unknown. In this study, mRNA sequencing was conducted in PBMC from VKH patients with active uveitis before treatment (n = 7), the same patients after prednisone combined with cyclosporine treatment (n = 7) and healthy control subjects strictly matched with gender and age (n = 7). We found 118 differentially expressed genes (DEGs) between VKH patients and healthy control subjects, and 21 DEGs between VKH patients before and after treatment. TRIB1 was selected as a potential biomarker to monitor the development of VKH according to the mRNA sequencing. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed to predict the possible biological functions and signaling pathways of DEGs. Neutrophil degranulation, peptidase regulator activity, secretory granule membrane, cellular response to peptide, growth factor binding and cell projection membrane were enriched as GO annotations of DEGs. Arachidonic acid metabolism and mitogen-activated protein kinase (MAPK) signaling pathway were potential signaling pathways involved in pathogenesis and drug response of VKH. A protein–protein interaction (PPI) network was constructed by STRING, and colony stimulating factor 1 receptor (CSF1R) was identified as the hubgene of all DEGs by Cytoscape. The cell type presumed to contribute to the aberrant expression of DEGs was analyzed with the use of publicly available single-cell sequencing data of PBMC from a healthy donor and single-cell sequencing dataset of monocytes from VKH patients. Our findings may help to decipher the underlying cellular and molecular pathogenesis of VKH and may lead novel therapeutic applications.