Dual role of complement in post-ischemic inflammation and recovery

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DESCRIPTION (provided by applicant): Ischemia/reperfusion injury (IRI) is a major clinical problem associated with several clinical conditions (e.g., hemorrhagic shock, severe burns, sepsis, myocardial infarction, stroke, transplant dysfunction/rejection). Complement is known to play a key role in sterile inflammation and injury following ischemia and reperfusion (IR), but more recently it has become evident that complement also plays important roles in tissue repair and regeneration following certain ischemic events. A goal of the proposed studies is to better understand the complement activation event following IR, and to dissect the dual role of complement effector mechanisms in IRI and tissue repair/regeneration. Concurrent with these goals, it is proposed to develop and characterize a novel targeted complement inhibitory strategy that protects against inflammation and injury while promoting tissue repair and regeneration. Previous and preliminary data indicate similar complement activation and effector mechanisms are involved in the injury and repair/regeneration processes of multiple organs and tissues. However, our model will be hepatic IRI and regeneration since mouse models have been well characterized and because of clinical significance. The overall working hypothesis is that complement is activated by natural self-reactive IgM that binds to neoepitopes exposed after ischemia, and that the terminal membrane attack complex (MAC) plays a key role in ischemia reperfusion injury (IRI) whereas more proximal activation products are important for repair and regeneration. We have isolated a panel of novel self-reactive IgM mAbs, and will use these mAbs to investigate immunological changes (neoepitope exposure) and the complement activation event that occurs after either IR or partial hepatectomy. We will also utilize complement inhibitors that function at different points in the cascade to investigate complement effector mechanisms involved in inflammation, injury and regeneration. We will also investigate the role of complement in phagocytic clearance of apoptotic and necrotic cells, and how this process impacts the inflammatory environment and subsequent tissue injury and repair. Finally, we will investigate how data generated in our mouse models relates to humans by analysis of clinical specimens. An additional goal of these studies is to develop a novel targeting strategy to locally deliver a complement inhibitor to post-ischemic neoepitopes utilizing single chain antibodies.