Plasmacytoid Dendritic Cells are the Primary Source of IFN-α During the Immunopathogenesis of Desiccating Stress-Induced Dry Eye Disease

Abstract

Purpose: Plasmacytoid dendritic cells (pDC) and derivative type I interferons (IFN-α/β) are important mediators of antiviral immunity and have also been implicated in autoimmunity. The contribution of TLR7/9 signaling in pDCs was evaluated during the immunopathogenesis of experimental Dry Eye.

Methods: Female C57BL/6 wild type mice, feeble (Slc15a4 mutants) and IFNAR1-/- mice were exposed to desiccating environmental stress (DS; subcutaneous scopolamine injections; humidity <40%; sustained air flow) for 10 days. A combination of flow cytometry, immunohistochemistry and ELISA were used to phenotype pDCs, IFN-α within the draining cervical lymph nodes (CLN) and ocular surface tissues over the course of disease.

Results: We previously demonstrated that pDCs were elevated in the draining CLN and ocular surface tissues of Dry Eye mice compared to controls, and that the higher frequency of pDCs correlated with enhanced IFN-α levels in the CLN and tears. To determine if pDCs are the main source of IFN-α, feeble mice (harboring a mutation in Slc15a4 required for endosomal TLR7/9 signaling in pDCs) and IFNAR1-/- (harboring fully functional pDCs, but non-responsive to IFN-α signaling) were evaluated during DS-induced Dry Eye. Indeed, feeble mice did not mount an IFN-α response to DS as tear levels (22.6±8.0 pg/ml) were similar to control (27.3±7.2 pg/ml); however, wild-type mice (58.1±11.6 pg/ml) and IFNAR1-/- (38.3±6.8 pg/ml) displayed significantly elevated IFN-α compared to matched controls (28.3±6.9 pg/ml and 12.1±3.3 pg/ml respectively).

Conclusions: Collectively, these data indicate that pDC are the primary source of TLR7/9-induced IFN-α during the development of DS-induced Dry Eye disease.

Keywords: 557 inflammation • 474 conjunctiva