IL-23 Promotes γδT Cell Activity in Dry Eye Disease Progression

PURPOSE: Conjunctival-resident γδT cells, the predominant ocular source of interleukin-17A (IL-17A), play crucial roles in dry eye disease (DED) pathogenesis. The upstream regulators of these cells are unknown. This study evaluated the role of conjunctival IL-23 expression in mediating γδT cell generation and elucidated its contribution to dry eye inflammatory responses. METHODS: Single-cell RNA sequencing (scRNA-seq) was used to identify and quantify conjunctival mRNA molecules in γδT cells in mice. The IL-23 level increased in wild-type (WT) and decreased in γδT-deficient (TCRδ-/-) mice after dry eye was induced via an intelligently controlled environmental system (ICES). Flow cytometry and transcriptome sequencing were used to investigate the impact of the changes in IL-23 expression on human γδT cells. RESULTS: The expression of the IL-23 receptor (IL-23R) was greater in γδT cells than in other conjunctival cell types, such as CD4+ T cells, CD8+ T cells and epithelial cells. An increase in IL-23 led to an increase in γδT cell density, which was proportional to dry eye severity. However, in the TCRδ-/- mice, the upregulation of IL-23 failed to increase the expression level of IL-17A and the severity of dry eye. Furthermore, increases in the expression of IL-23 and the number of γδT cells were evident in the ocular surface cells of patients who developed visual display terminal syndrome. CONCLUSIONS: An increase in conjunctival IL-23 expression contributes to the induction of the DED inflammatory response through interactions with its cognate receptor on γδT cells and the promotion of their proliferation. The findings of this study suggest that the suppression of IL-17A through the blockade of IL-23R activation may be a viable target for improving the management of inflammation in DED patients.