Antibody Deposits in Retina Correlate With Loss of Retinal Ganglion Cells in an Experimental Autoimmune Glaucoma Model

Abstract

Purpose: : In the Experimental Autoimmune Glaucoma (EAG) model retinal ganglion cell (RGC) loss is caused by immunization with neuro-retinal antigens. The aim of this study was to examine if this RGC loss correlates with accumulation of antibodies in the retina.

Methods: : Rats were immunized with bovine retinal ganglion cell-layer homogenate (RGH; n=10) or myelin basic protein (MBP, n=10) in combination with pertussis toxin (PTX) and incomplete Freund’s adjuvant (IFA). Animals received a booster immunization after 4 weeks. A control group (Co, n=10) received only PTX and IFA. All animals were euthanized after 6 weeks. In a 2 week study animals were immunized with MBP (n=5) or bovine optic nerve homogenate (ONH; n=5).The left eye of each animal was used for RGC count after staining with cresyl. In the right eye antibody deposits were detected in cross-sections via anti-rat-IgG or anti-rat IgM stain. Deposits were manually counted on one entire cross-section of each retina cut transversally through the papilla. Data were analyzed by ANOVA and post hoc test.

Results: : In both studies significant RGC loss was observed in rats immunized with ONH (P=0.016), RGH (P=0.006), or MBP (P=0.017 after 2 weeks; P=0.018 after 6 weeks). After 6 weeks an average of 330.9 RGCs was counted in controls in contrast to 303.5 in all immunized animals.IgG-antibody accumulation could be detected in retinae of immunized rats with a mean count of 26.2 for RGH, 15.2 for MBP, and 10.7 for controls (after 6 weeks). The amount of antibody deposits was significantly higher in RGH animals than in controls (P=0.01). IgG-deposits were mainly located in peripheral areas of the ganglion cell layer. The number of deposits in MBP animals was not significantly different (P=0.77). IgM deposits could be observed epiretinally 2 weeks after immunization.

Conclusions: : Significant RGC loss as well as specific antibody accumulation patterns could be observed after systemic immunization with ONH, RGH or MBP. These studies demonstrate that neuro-retinal antigens cause an accumulation of antibodies in the retina, which may play an important role in the pathogenesis of RGC loss in the EAG model. In this model retinal antibodies could capture membrane receptors of ganglion cells which influence important physiological functions such as communication and supply deliverance.

Keywords: retinal degenerations: cell biology • immunohistochemistry • ganglion cells