IL-18 receptor axis in allergic conjunctivitis: a multi-omics study

The pathophysiology of allergic conjunctivitis (AC) is not fully explained by the traditional Th2-centric model. This study aimed to identify AC-associated candidate genes and delineate immune pathways, with a focus on cell-type-specific mechanisms that could contribute to disease heterogeneity.

We employed an integrative multi-omics strategy, using three genomic analyses (FUSION, MAGMA, UTMOST) on human GWAS data to identify AC-associated candidate genes. These candidates were then investigated using single-cell RNA sequencing data from a mouse model of AC to map immune cell communication and signaling dynamics. Key pathways were validated in an independent ovalbumin-induced AC mouse model using clinical scoring, qRT-PCR and Western blot analysis.

This approach identified nine high-confidence AC-associated candidate genes, including key components of the IL-1 and Toll-like receptor families. In the AC mouse model, the IL-18 receptor components Il18r1 and Il18rap were selectively upregulated in NK and T cells from allergic versus control mice and correlated positively with interferon-γ (Ifng) expression. Cell-cell communication and pseudotime analyses indicated an allergic-state network characterized by enhanced NK cell-linked IFN-γ signaling to antigen-presenting cells and dynamic changes in NF-κB and JAK-STAT pathway activity. In the OVA-induced model, conjunctival IL-18, IL-18R1, IL-18RAP and phosphorylated NF-κB p65 were increased in AC versus controls and showed a stepwise rise across mild, moderate and severe clinical groups.

Across human genetics, single-cell transcriptomics and in vivo validation, an IL-18 receptor/IFN-γ axis in NK and T cells emerges as a reproducible module associated with AC and its severity. These findings extend the immunopathological framework of AC beyond a purely Th2-driven process and nominate IL-18R-linked signaling as a candidate pathway for future mechanistic and therapeutic studies.