Abstract
Abstract: :
Purpose: Despite an apparent lack of lymphatic vessels, antigen from the anterior chamber of the eye is found in lymph nodes draining the orbit. Using fluorescent beads to identify phagocytic cells, we investigated whether these antigen-presenting cells migrate to draining lymph nodes. Methods: Fluorescent beads (about 300,000, 2µm diameter) or 150µg soluble fluorescent ovalbumin (OVA) were injected in 2-4µl of saline either into the anterior chambers or intradermally into the ear pinnae of BALB/c mice. MHC class II+ cells ingesting the beads or fluorescent OVA were identified by fluorescent and immunochemical histology. The movement of these labeled cells in the iris or skin was monitored by time-lapse intravital microscopy, recorded for at least 1 hour beginning at 4, 12, 24 and 48 hours after injection. The arrival of fluorescent dendritic cells (CD11c+ MHC class II+) in the mandibular and superficial cervical lymph nodes draining both the eye and ear was investigated by flow cytometry. Results: Dendritic cells labeled with fluorescent OVA can be found in the mandibular and superficial cervical lymph nodes draining the orbit 24 hours after anterior chamber injection of the fluorescent protein. In contrast, phagocytes that take up beads injected into the anterior chamber are not found in the draining lymph nodes. However, bead-containing dendritic cells are found in the draining lymph nodes 12 hours after intradermal injection into the ear pinnae. Cells in the iris that have ingested beads or ovalbumin exhibit no detectable movement out of the iris in time-lapse movies taken 12, 24 and 48 hours after challenge. The migration of labeled cells via lymphatics is distinctly observed in the ear, peaking 12 hours after intradermal injection of beads. Conclusion: In contrast to their behavior in skin, phagocytic cells, including dendritic cells, that take up beads injected into the anterior chamber were not observed entering lymphatics and do not accumulate in regional lymph nodes. We hypothesize that immunogenic antigen in the anterior chamber is not presented in the lymph nodes by local antigen-presenting cells but that antigen leaking out of the eye via the uveoscleral route is taken up by conjunctival dendritic cells.
Keywords: 513 phagocytosis and killing • 431 imaging/image analysis: non-clinical • 318 anterior segment