Abstract
Purpose :
Increased prevalence of dry eye is found with aging. Dendritic cells (DCs) are professional antigen presenting cells that have a pivotal role in mediating both tolerance and immunity and their functional changes have been reported in aging. The purpose of this study was to evaluate if functional changes in aged female DCs correlated with greater priming of Th (T helper) 1 cells.
Methods :
Female 8 week and 24 month-old C57BL/6 mice were used. Visualization of CD11c+, CD11b+ CD11c+MHCII+ and CD11b+MHC II+ cells was performed in wholemount conjunctivas (CJ) and quantified by flow cytometry in CJ. The fraction of young and elderly CJ DCs and fresh isolated cervical lymph node (CLN) cells with high expressing aldehyde dehydrogenase (ALDH) activity was quantified by flow cytometry using a commercial Aldefluor kit. Uptake of fluorescent antigen OVA (45kDA) was investigated by laser scanning confocal microscope using the Z-stack option in wholemount CJ. Recovery of OVA+laden DCs was evaluated by flow cytometry in CLN 3 and 24 hours after topical administration of OVA and OVA 323-339 peptide. OVA-peptide presentation to CD4+T cells from OVA OT II transgenic mice was evaluated using CLN cell suspension from young and old mice. T-cell-related cytokine expression was examined by quantitative polymerase chain reaction 72h later.
Results :
Aged mice have greater frequency of CD11c+ and CD11b+ cells in cornea and conjunctiva, but significantly lower frequency of CD11b+MHC class II antigen DCs than young female mice (P<0.05). CJ monocytes (DCs and macrophages) had greater ALDH activity, reflecting high retinoic acid synthesis capacity, than CLN monocytes in all ages, and aged female were greater than young female. Increased diffusion of OVA through the conjunctival stroma was seen in aged females. This was accompanied by greater and faster uptake of full OVA and OVA-peptide by aged DCs. CD4+T cells primed by aged CLN DCs had significantly increased IFN-γ transcripts than young CLN DCs.
Conclusions :
Even though aged DCs have a more immature phenotype, paradoxically they showed greater migration to the CLN and greater Th1 polarizing activity. This data suggest that dysfunction of DCs that occurs with age may play a pivotal role in the pathogenesis of dry eye disease.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.