Abstract
Purpose: :
Chemokine receptor 6 (CCR6) coordinates migration of Th-17 cells. Our previous studies have demonstrated the requirement of Th17 cells in the pathogenesis of dry eye disease. The objective of this study was to evaluate the role of CCR6 in the migration of Th17 cells in an experimental model of dry eye.
Methods: :
Desiccating stress (DS) was induced by subcutaneous injection of scopolamine and exposure to a drafty low humidity environment in CCR6 knock-out (CCR6KO) and wild-type (WT) mice, aged 6-8 weeks for 1, 5 or 10 days (DS1, DS5, DS10). IL-17A-producing cells were evaluated by ELISPOT in CD4+ T cells isolated from cervical lymph nodes (CLN) or in cells isolated from cornea and conjunctiva. Corneal barrier function was assessed using fluorescent Oregon-Green Dextran (OGD). Conjunctival goblet cell density was counted in periodic acid Schiff stained sections. Immunohistochemistry evaluated CD4 cell infiltration of the conjunctiva.At DS5, CD4+T cells from spleen and cervical lymph nodes were isolated and adoptively transferred into Rag1-/- mice and results compared to WT donor mice. Matrix metalloproteinase (MMP-P)-3 and -9, IL-17A, IFN-γ were evaluated by real time PCR.
Results: :
Lymphocytes found on the ocular surface (OS) and draining lymph node expressed CCR6, and increased expression was found in response to DS in WT mice. CCR6KO mice after DS showed a decrease in the number of infiltrating CD4+ T cells in the conjunctiva epithelium that was accompanied by an increase in filled goblet cells and normal corneal barrier function. CCR6KO mice had similar number of Th-17+ cells in the CLN, but very few on the ocular surface, demonstrating their inability of Th-17+ cells to migrate to the eye after priming in the lymph nodes. Confirming these results, CD4+ T cells from CCR6KO mice adoptively transferred to immunodeficient mice were unable to reach to the OS as effectively as CD4+ T cells from WT mice in response to DS. Similar to CCR6KO donor mice, RAG-/- recipients showed increased GC density and lower CD4+T cell infiltration in the conjunctiva. In contrast to WT recipients, CCR6KO recipient mice were unable to upregulate MMP-3, MMP-9 mRNA transcripts in cornea and IL-17A, IFN-γ mRNA transcripts in conjunctiva.
Conclusions: :
CCR6 is needed for the recruitment of Th17 cells to the ocular surface to mediate pathogenesis of dry eye.
Keywords: cytokines/chemokines • immunomodulation/immunoregulation • cell-cell communication