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P. Laspas, S. C. Joachim, O. W. Gramlich, P. F. Gottschling, C. Cuny, N. Pfeiffer, F. H. Grus; Immunization With Ocular Antigens Leads to Loss of Retinal Ganglion Cells and Increased Immunoreactivity Against Ocular Tissues. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3646.
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© ARVO (1962-2015); The Authors (2016-present)
In an animal model of Experimental Autoimmune Glaucoma, loss of retinal ganglion cells (RGCs) is conducted through immunization with ocular antigens. Aim of this study was to examine if this RGCs loss could be related to increased antibody reactivity against ocular tissues.
An optic nerve homogenate (ONH) was used to immunize two groups of rats with a high (ONH I, n=5) and a low (half) antigen dose (ONH II, n=5). An additional group received an immunization with keratin (KER, n=5) and the control group only NaCl (CO; n=5). Antigens were mixed in Freund’s adjuvant plus Pertussis toxin. Animals were scarified four weeks later, retinal flatmounts were prepared and ganglion cells counted in 4 predefined areas. Before immunization, as well as two and four weeks afterwards, serum samples were obtained. Retina and optic nerve cross-sections from healthy animals were incubated with these samples followed by anti-IgG antibody and DAB. Staining intensity was scored from 0 (no staining) to 3 (severe) by 3 examiners. Statistic analysis using ANOVA and post-hoc tests followed.
Animals immunized with ONH had lower density of retinal ganglion cells in comparison to the CO group (P=0.03 for ONH I; P=0.009 for ONH II). Animals of the keratin group demonstrated similar densities as controls (P=0.6). No inter-group difference in IgG reactivity was detected before and 2 weeks after immunization (P>0.05). Elevated IgG antibody reactivity against ocular tissues was found in ONH animals at 4 weeks. The mean scores of the ONH I groups were 2.4±0.4 for retina (P=0.002) and 2.5±0.4 for optic nerve cross-sections (P=0.0001). The ONH II group had a mean score of 1.9±0.9 for retina (P=0.01) and 1.7±1 for optic-nerve (P=0.0001). The KER group revealed no difference in mean scores compared to CO regarding retina (KER=0.5±0.8; CO=0.3±0.3; P=0.9) or optic nerve sections (KER=0.3±0.6; CO=0.1±0.1; P=0.99).
Immunization of rats with ocular antigens leads to an increased IgG antibody reactivity against ocular tissues as well as RGC loss. These antibodies are capable of binding to retina and optic nerve and possibly trigger RGC death in this model. Immunization with a non-ocular antigen (KER) neither leads to RGC loss nor increased immunoreactivity, which further proves that these phenomena are specific for ocular antigens.
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