Characterization of antigen-presenting cells in fresh and cultured human corneas using novel dendritic cell markers.

Adult healthy human corneas bear a distinctive number of antigen-presenting cells (APCs) important for the fate of a graft. The purpose of this study was to differentiate between Langerhans cells (LCs) and other dendritic cells (DCs) and between mature and immature APCs in fresh and cultured human corneas using specific markers. Immunofluorescence double staining was performed for Langerin/CD207, CD1a, DC-SIGN/CD209, DC-LAMP/CD208, CD45, CD11c, CD11b and HLA-DR. Langerin(+)/CD1a(+)/HLA-DR(+) LCs (approximately 100 cells/mm(2) in fresh corneas) were found in the limbal and peripheral regions of corneal epithelium and the anterior stroma up to 83 days of culture. All these cells coexpressed CD45 and CD11c. DC-SIGN(+)/CD45(+) DCs (approximately 150 cells/mm(2) in fresh corneas) were detected mainly peripherally and in the anterior stroma, even in long-term cultured corneas. Most of these cells were HLA-DR(-). Few mature DCs (DC-LAMP(+)/HLA-DR(+)) were found in fresh and cultured corneas. Macrophages (CD11c(-)/CD11b(+)) were seen in the peripheral, paracentral, and even central regions of the posterior stroma. This is the first demonstration that human corneas harbor populations of Langerin(+)/CD1a(+)/HLA-DR(+) LCs and DC-SIGN(+) DCs in a distribution pattern similar to that in the skin. Few APCs are in a mature state (DC-LAMP(+)). Given the reduced but not complete depletion of APCs during organ culture, these grafts still bear a potential risk for rejection.