NK Cells Promote Th-17 Mediated Corneal Barrier Disruption In Dry Eye

Abstract

Purpose: : Natural killer (NK) and natural killer T cells (NKT) cells reside in normal conjunctiva. As one arm of innate immunity, these cells can respond rapidly to stress situations. The purpose of this study was to investigate the role of NK/NKT in the induction of dry eye disease using a murine model of dry eye.

Methods: : Desiccating stress (DS) was induced by subcutaneous injection of scopolamine and exposure to a drafty low humidity environment in C57BL/6 (B6) mice, aged 6-8weeks for 1, 5 or 10 days (DS1, DS5, DS10). A separate group of mice received anti-NK antibody intra-peritoneal injection (100µg/mouse, clone NK1.1) at days -4,-2, 0 and +2 of desiccating stress. Dendritic cell number and activation was evaluated by flow cytometry analysis of cervical lymph node (CLN) cells. ELISPOT was used to meaure the number of IL-17-producing CD4+ T cells in CLN. At DS5, CD4+T cells from spleen and cervical lymph nodes were isolated and adoptively transferred into C57BL/6 nudes. After 72 hours, corneal barrier function was assessed and whole cornea was lysed for gene expression analysis. These results were compared to an isotype-injected control group.

Results: : During DS for 10 days there was a significant progressive increase in both number and MHC class II positive CD11c and CD11b dendritic cells in the CLN. Systemic depletion of NK cells prior to and during DS5 led to a decrease in the frequency of total and activated dendritic cells and a decrease in number of T helper-17 cells in the CLN. B6.nude recipient mice of adoptively transferred CD4⁺T cells isolated from NK-depleted DS5 donor mice showed significantly less corneal barrier disruption, less upregulation of matrix metalloproteinase -3 immunoreactivity and gene expression and lower levels of IL-17A and CCL20 in the cornea epithelia compared to recipients ofl CD4⁺T cells from isotype antibody-injected mice.

Conclusions: : Taken together, these results show that the NK/NKT cells are involved in the acute immune response to desiccation-induced dry eye by activating dendritic cells, which in turn coordinate generation of the pathogenic Th-17 response.

Keywords: cornea: tears/tear film/dry eye • conjunctiva • cytokines/chemokines