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U. Lehmann, H. Roehrich, N. D. Heuss, D. S. Gregerson; Identification, Characterization, and Functional Analysis of Dendritic Cells in Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3626. doi: https://doi.org/.
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Activation of T cells for protective, pathogenic or regulatory roles requires antigen presenting cells (APCs). Dendritic cells (DC) are fundamentally important in antigen presentation, but have been difficult to study in retina. CD11c is among the most reliable surface markers for DC. Using transgenic mice in which the CD11c promoter drives expression of green fluorescent protein (GFP) and diphtheria toxin receptor (DTR), it is possible to both deplete and visualize DCs in retina.
Administration of DTx in various doses and by different routes was done to dissect DC processes in retina. In some experiments, DTx was injected (1 uL) into the anterior chamber (AC) of the eye of DTR-Tg mice to achieve local depletion. At specified times post-inoculation, retinas were harvested, lightly fixed, and stained with antibodies. Whole retina was flat-mounted and analyzed by fluorescence microscopy. Cervical and submandibular LNs were also analyzed. Retina blood vessels were stained with isolectin B4 to examine CD11c cell distribution and association with blood vessels.
Depletion and recovery of CD11c cells in retina after administering DTx by IV, IP or AC routes was DTx dose and time dependent. Depletion in retina was rapid and transient, showing that toxin readily penetrated the blood/retina barrier, and that the depleted DC were rapidly replaced. Control eyes injected with saline in the AC showed a rapid, substantial increase in the number of retinal CD11c cells. To examine the role of injury, eyes were given a small tear in the iris, which also lead to substantial elevation in retinal DCs. The sensitivity of retinal DC counts to injury was confirmed by use of a partial optic nerve crush, which also led to a large increase in retinal CD11c cells.
Our studies show that retina is a highly dynamic environment in which CD11c cells change rapidly in response to even very minor injury, including a simple 1 uL injection of saline into the AC. These results have important implications for the interpretation of immune deviation processes resulting from intraocular inoculations, and for studies involving reconstitution of retinal APC by irradiation and bone marrow grafting.
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