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P.G. McMenamin, A.S. Voon, W. Colangello, S. Camelo; Fluorescent Labelled Antigen Uptake in the Anterior Segment and Distribution to Secondary Lymphoid Organs . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4302.
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Purpose: The aim of this study was to determine the capacity of iris resident bone marrow-derived cells to capture fluorescent-labelled antigen (Ag) injected into the anterior chamber (AC) of the rat eye and to examine the drainage pathways of Ag from the eye and its subsequent distribution in secondary lymphoid organs. Methods: Three experiments were performed: (1) single injection of cascade blue-labelled Dextran (CB-D) (70kD) into the right eye of 8-11 week-old Lewis female rats, (2) double fluorescent injection (CB-D injected into the right eye and FITC-D (40kD) in the left eye), (3) CB-D injected into the right eye and FITC-D in the tail vein. Kinetic of migration of iris Ag-positive cells was examined using in vivo video fluorescence microscopy. Twenty-four hours after AC injection animals were perfusion fixed and ocular tissues were examined by either frozen sections, paraffin sections or wholemounts using a range of monoclonal antibodies to determine the phenotype of Ag-positive cells. Ssubmandibular lymph nodes (SMLN), cervical lymph nodes (CLN), mesenteric lymph nodes and spleen were frozen and sections analysed by confocal microscopy. Results:24 hours post-injection cells in the iris, ciliary body, anterior suprachoroidal space, iridocorneal angle and limbal episcleral tissue had internalised CB-D. These cells expressed combinations of macrophage and dendritic cell markers (ED1, ED2, ED3, OX62) but rarely OX6 (MHC class II). The number of Ag+ cells decreased over time but they were still detectable after 12 days. 24 hours after intracameral injection Ag+ cells were situated in the subcapsular sinuses in the SMLN, CLN, and in the marginal zone of the spleen. After bilateral ocular injections CB-D and FITC-D double Ag+ cells were found in the subcapsular sinuses in the right CLN, and in the marginal zone of the spleen. Following ocular (CB-D) and intravenous (FITC-D) injections double-labelled cells were found in the right SMLN, right CLN and spleen. Conclusions: Intracameral Ag is taken up predominantly by resident tissue macrophages in the uveal tract and may be retained in the anterior uvea for some time. Ag also appears to exit the eye via the conventional and non-conventional aqueous outflow routes, the latter supporting the hypothesis that anterior chamber-derived Ags have access to draining lymph nodes via conjunctival/orbital lymphatics. Double Ag+ cells in the spleen and local lymph nodes after ocular/IV injections also suggests that Ag travels from the eye to secondary lymphoid organs in a soluble form via the blood.
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