The long-term goal is to understand the fundamental basis of complement signaling in the eye, and how misregulation in this process leads to pathology, to ultimately aid in the development of therapeutic ap- proaches for devastating blinding diseases. BrM, a pentalaminar extracellular matrix compartment, contains a middle elastic layer (contains elastin, EL). Thickness and integrity of this EL is thinner and less abundant in the macula than in the periphery; a discrepancy that is more severe in early AMD and active choroidal neovascularization (CNV). AMD patients have elevated serum EL-peptide and anti-EL antibody levels; and EL-peptides can increase choroidal endothelial cell migration, overall suggesting that abnormalities in EL homeostasis play a role in AMD. We have characterized a mouse model of smoke-induced ocular pathology (SIOP) in C57BL/6J mice. These mice exhibit increased serum levels of anti-EL antibodies (Abs, IgG2a), and show a complete loss of integrity of the elastic layer. Conversely, mice immunized with oxidized EL (neoepitope) develop more severe vision loss and pathology in BrM when compared to those immunized with control EL (self-protein). We are guided by our overall hypothesis that age- and/or stress-dependent increase in elastase activity leading to elastin degradation and coordinated production of (anti) α-elastin Abs are early events in AMD. We further hypothesize that α-elastin Abs binding to FcγRs trigger antibody- dependent cell-mediated cytotoxicity, exacerbating AMD pathology, a mechanism that is amplified by com- plement-dependent cytotoxicity. Also, we suggest that alpha-1 antitrypsin (A1AT), an endogenous elastase inhibitor, can be utilized to retain BrM integrity as a potential early AMD therapy. Three specific aims are designed to determine the involvement of antibodies against elastin in BrM pathology in mouse models, and second to test the prediction that A1-AT reduces pathobiology in mouse and man, using A1-AT for thera- peutic purposes in mouse models and analyzing the MarketScan Database for A1-AT use and AMD onset. The novelty of the idea is that elastase activity results in structural pathological changes (elastin loss, in- flammation), and it is highly innovative that an existing elastase inhibitor will be tested for its ability to pre- serve BrM integrity, as a treatment paradigm to slow down the progression of disease early in the process.