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

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

Methods: 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.

Results: 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.

Conclusions: 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.