Distinct populations of dendritic cells in the normal human donor corneal epithelium

To characterize dendritic cells (DC) in normal human corneal epithelium.

Normal human donor corneal epithelium was examined by fluorescence microscopy with single and double staining for multiple markers. Morphologic studies were also performed by confocal microscopy. HLA-DRa, CD1c, and CD16 mRNA expression in the corneal epithelium was examined by RT-PCR. CD45+ cells were separated from the corneal epithelium with magnetic beads and then were stimulated with TNF-alpha and lipopolysaccharide in vitro.

CD45+ cells were mainly located in the basal-cell layer of the corneal epithelium and partly in the wing/surface layers. CD45-positive cell numbers were significantly higher in the peripheral cornea (3-6 mm from the center) than in the central cornea (0-3 mm from the center). All these cells expressed HLA-DR and CD11c but not CD3, CD11b, CD14, CD19, CD56, or CD66, suggesting that these were bone marrow-derived myeloid DC. Some DR+CD11c+ DCs from the periphery expressed CD1c and CD16. HLA-DRa, CD1c, and CD16 mRNAs were detected in normal corneal epithelium. These CD11c+ DCs did not express CD123, CD1a, DC marker (CMRF56), CD40, CD80, or CD86. When CD45+ cells were isolated from the corneal epithelium by magnetic cell sorting, CD40 and CD86 expression were detected after in vitro stimulation with TNF-alpha and lipopolysaccharide.

These findings demonstrate that normal human corneal epithelium contains at least three DC phenotypes, with HLA-DR+ myeloid lineage CD11c+CD16- DCs as the main population plus a small number of CD11c+CD16+ DCs and CD11c+CD1c+ DCs. These cells can be discriminated from bone marrow-derived cells in the human corneal stroma.