Abstract
Purpose: :
A novel murine model of immune-mediated retinal degeneration previously described an immune response to carboxyethylpyrrole (CEP)-adducted proteins that results from age-related oxidative stress. This project aims to quantitatively and qualitatively characterize the differences and kinetics in the recruitment of inflammatory cells and severity of retinal lesions between different strains of mice.
Methods: :
C57BL/6 and BALB/c mice were immunized with CEP-MSA, non-adducted MSA emulsified in complete Freund’s adjuvant (CFA), or CFA only for both strains. At day 10 the mice were challenged with incomplete Freund’s adjuvant-CEP-MSA, followed by a second challenge with CEP-MSA at day 40. Eyes were harvested for histology and immunohistochemistry analysis at early (2-3 months), intermediate (4-5 months), and late (7-10 months) time points post-immunization for each corresponding mouse. Eyes for histology were fixed in 2% Paraformaldehyde and 2.5% Glutaraldehyde in 0.1M PO4 buffer (pH = 7.4) overnight and dehydrated in graded ethanol and propylene oxide. After polymerization in a resin mixture, 0.7µm-thick serial sections were cut from each eye and stained with toluidine blue. Identification of inflammatory cell recruitment to retinal lesions (neutrophils, NIMPR14; macrophages, CD11b and B cells, CD19) was done by immunohistochemistry.
Results: :
A stronger inflammatory cell recruitment localized in retinal mid-peripheral segments as well as greater retinal photoreceptor cell nuclei migration in BALB/c immunized mice than in naïve mice correlates with higher CEP autoantibody serum levels at early time points. Enhanced cell recruitment is observed at intermediate time points in both immunized and naïve mice with higher cell infiltration in the immunized mice. In turn, C57BL/6 mice show relatively low inflammatory cell recruitment compared to BALB/c mice in both immunized and naïve mice although there are noticeable changes in the photoreceptor layer of immunized mice.
Conclusions: :
The variations in inflammatory cell recruitment between BALB/c (Th2 prone) and C57BL/6 (Th1 prone) mice suggest that disease is mediated by different immune mechanisms in each mouse strain. The progressive development of pathology observed in BALB/c mice correlated to higher inflammatory cell recruitment and CEP autoantibody titers in immunized mice suggests a complementary role of CEP autoantibodies and aging in the pathological development of oxidative stress-mediated autoimmune disease.
Keywords: age-related macular degeneration • autoimmune disease • inflammation