Abstract
Purpose: :
Carboxyethylpyrrole (CEP)-modified proteins in drusen and CEP autoantibodies are associated with AMD. By immunizing mice with CEP-adducted mouse serum albumin (CEP-MSA), our lab has developed a mouse model with AMD-like pathology. The immunological characterization of our AMD model will generate new insights into the biology and possible treatment of this disease by providing a mechanistic link between oxidative stress and complement activation.
Methods: :
Either C57BL/6 or BALB/c mice (including a variety of gene targeted mutant strains) were immunized with CEP-MSA and complete Freund’s adjuvant (CFA). At different time points post-immunization, serum was isolated to measure CEP antibody titers by ELISA. At harvest, eyes were prepared for histology and immunohistochemistry while spleens were removed to perform ex vivo stimulation with CEP-MSA and for T cell assays. Cytokine production was measured by ELISA and/or intracellular staining. Flow cytometry was also used for phenotypic analysis of responding cells. For control comparisons we used mice immunized with sham-adducted MSA, CFA only or age-matched naïve mice.
Results: :
CEP autoantibody serum levels correlate with retinal damage and ex vivo T cell activation. CEP-specific CD4+ T helper (Th) and CD8+ cytotoxic T lymphocytes (CTL) become activated upon restimulation with CEP-MSA and express the pro-inflammatory cytokines IFN-γ and interleukin-17 (IL-17). Activated CTL are particularly responsive to IL-2 in these cultures. Analysis of mice lacking specific T cell lineages points to a primary role for Th17 cells. On the other hand, B cell deficient mice show enhanced retinal lesions compared to wild type mice.
Conclusions: :
The presence of retinal lesions in mice lacking CEP autoantibodies suggests that AMD-like pathology is antibody-independent, therefore autoreactive T cells may be the crucial effector cells leading to the underlying retinal degeneration observed in CEP-MSA immunized mice. Our results provide novel insight regarding adaptive immunity in the development of AMD that could lead to improved diagnosis and treatment of this serious blinding disease.
Keywords: age-related macular degeneration • autoimmune disease • inflammation