Type III interferons attenuates Th1/Th17 cell pathogenicity and regulates retinal pigment epithelium cells via NLRP1/NLRP3 signaling axis in autoimmune uveitis.

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.