Phenotypes, distribution, and morphological features of antigen-presenting cells in the murine cornea following intravitreal injection

Purpose: To study the phenotypes, distribution, and morphologies of different antigen-presenting cells (APCs) in the murine cornea. Methods: Intravitreal injection of fluorescently tagged ovalbumin (OVA) or antibodies to MHC-II (I-A^d), F4/80, CD11c, B7-1, and B7-2 was performed to label cells in the murine cornea. Light and transmission electron microscopy were used to examine corneal histology. Intravital microscopy, epifluorescence microscopy, and confocal microscopy were used to evaluate the labeled cells. In vitro staining was performed to validate the in vivo staining and localize the labeled cells. Three-dimensional rotatable images were taken to evaluate relationships between two differently labeled cells. Results: Histological examination revealed no observable change in the cornea following intravitreal injection. In vivo staining showed that OVA⁺ cells and cells positive for MHC-II, F4/80, CD11c, B7-1, or B7-2 were noted throughout the cornea with a decreasing density from limbus toward the central cornea. Two populations with distinct morphological features were identified among these APCs. Labeled cells were found beneath the epithelium or in the shallow stroma in the central and paracentral cornea, but in all layers in the peripheral cornea. A number of F4/80⁺ and CD11c⁺ cells were also positive for OVA, MHC-II, B7-1, or B7-2. Rotatable images showed a close contact between two differently labeled cells. Conclusions: Intravitreal injection of labeled antibodies can be adapted to visualize labeled cells in the cornea. APCs with distinct morphologies, phenotypes, and distribution may contribute to the immunologically privileged feature of the cornea.