Purpose: The purpose of this study was to determine the quantity and distribution of antigen presenting cells (APC) in various inflammatory and non-inflammatory corneal diseases, comparing in vivo confocal microscopy (IVCM) and immunohistochemistry.
Material and methods: Corneae of 41 eyes, composed of group 1 (status post herpes-keratitis), group 2 (keratoconus) and group 3 (graft rejection after keratoplasty) were investigated. IVCM was used preoperatively to assess the distribution and density of dendritic cells in the corneal center versus the paracentral area. Afterwards, all patients underwent penetrating keratoplasty. The host corneas were analyzed by immunohistochemistry for antigen presenting cell distribution, density and characterization by using specific markers for CD207/Langerin, CD209/DC-SIGN and HLA-DR. The IVCM findings were compared with immunohistochemistry results in the corneal epithelium.
Results: Cells with branching dendritic morphology were visualized by IVCM mainly in the basal epithelial layer and subepithelial nerve plexus of the central and paracentral cornea. The density of APC in IVCM decreased in all groups towards the central part of the cornea. The highest gradient was observed in group 2, followed by groups 1 and 3. The corneal paracenter showed similiar distribution of APC in group 1 and 2 (76.7 cells/mm(2) and 74.4 cells/mm(2)). The highest density of central APC was observed in group 1 (53.76 cells/mm(2)), followed by group 3 (27.0 cells/mm(2)) and group 2 (24.2 cells/mm(2)). In immunohistochemistry positive stained, APC were distributed similarly to IVCM but with a higher density (p < 0.05).
Conclusion: Distribution, density and stage of maturation of corneal epithelial APCs can be evaluated on morphological basis by IVCM. However, the corneal APCs density was about three-fold lower compared to immunohistochemistry findings.