Abstract
Purpose: :
Plasmacytoid dendritic cells (pDCs), a distinct type of bone marrow (BM)-derived DCs, play an important role in linking innate and adaptive immune responses. pDCs are important mediators of antiviral immunity through their ability to produce large amounts of type I interferons on viral infection. To date, little is known about the presence and nature of pDCs that reside in the cornea. The purpose of this study was to investigate the phenotype and distribution of pDCs within the normal and inflamed murine cornea.
Methods: :
Single cell suspensions of liberase-digested corneas were pooled, prepared and stained for an array of conventional DC (cDC) and pDC markers. Further, normal and inflamed corneas of C57BL/6 mice were excised at different time points after inflammation, and immunofluorescence triple-staining with antibodies against B220, PDCA-1, CD11c, CD11b, CD19, CD45, toll-like receptor 7 (TLR-7) and TLR-9 was performed by confocal microscopy on whole-mounted corneas, in order to characterize phenotype, distribution, and density of pDCs.
Results: :
pConfocal microscopy demonstrated that CD45+B220+PDCA-1+ pDC reside in the anterior stroma and basal epithelium of both the central and peripheral cornea. The density of pDCs increased from the center (70/µm2) towards the periphery (120/µm2) in the basal epithelium, while it did not change in the anterior stroma (65/µm2). During inflammation, there was a two-fold increase in pDC density in the anterior stroma and peripheral epithelium, with a three-fold increase in the central epithelium. Corneal pDCs expressed both TLR-7 and TLR-9. Further, a very small population of B220+CD11c+ cDCs was present in anterior corneal stroma, which was negative for PDCA-1- and CD19 (B cells). Flow cytometery of digested single cell suspensions of the cornea confirmed the presence of pDCs .
Conclusions: :
This study demonstrate that, in addition to previously characterized cDC and macrophages, the cornea is endowed with a resident population of pDCs in the anterior cornea. The unique innate immune functions of pDCs are crucial both in infectious diseases and in autoimmune diseases.
Keywords: antigen presentation/processing • cornea: basic science • microscopy: light/fluorescence/immunohistochemistry