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Stephanie C. Joachim, Oliver W. Gramlich, Panagiotis Laspas, Sandra Kuehn, Harald D. von Pein, Burkhard Dick, Franz H. Grus; Increased Immune Response Against Ocular Tissue After Immunization With An Optic Nerve Antigen. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6941.
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Until now it is not known if antibodies detected in patients with glaucoma are harmful to retinal ganglion cells or trigger disease formation in any way. In a model of experimental autoimmune glaucoma retinal ganglion cell (RGC) loss can be induced through immunization with certain ocular antigens.
Rats were injected with optic nerve homogenate (ONA, n=11) in Freund’s adjuvant (FA) and pertussis toxin (PTX; both Sigma-Aldrich). Animals of the control group (CO, n=9) received FA and PTX in sodium chloride. Booster injections were given after 4 and 8 weeks. Intraocular pressure measurements were performed throughout the study using a Tonopen. Serum from different study points was used to analyze the occurrence of autoreactive antibodies against retina or optic nerve tissue. The antibody staining intensity was scored by 3 examiners from 0 (=no) to 3 (=severe stain). For each point in time p-value was calculated via student t-test. 10 weeks after immunization RGC density was evaluated via retinal flatmounts. Additionally brain sections were evaluated for possible pathological findings using H&E and LFB stain and antibodies to CD68 and CD45 (after 12 and 70 days).
Ocular pressure stayed within the normal range (CO=15.3mmHg; ONA=14.8mmHg; p=0.9). A continuous increase of autoreactive antibodies against optic nerve as well as retina sections could be observed. At 4, 6 and 10 weeks antibody reactivities were significantly higher in immunized animals (p<0.01). The following mean scores were recorded at 10 weeks for retina: CO: 0.3±0.1; ONA: 2.2±0.2 (p=0.00001) and optic nerve: CO: 0.3±0.2; ONA: 2.7±0.1 (p=0.00001). Density of RGCs was significantly decreased in ONA animals (p=0.009), especially in peripheral regions of the retina (p=0.003). No pathologic finding was noted on brain sections, no mononuclear cell infiltrates consisting of macrophages or lymphocytes were detectable.
Our findings suggest that these antibodies play a substantial role in the mechanisms leading to retinal ganglion cell death. This autoimmune model should be helpful to develop more causative glaucoma therapies.
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