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Immune Response
Vertebrates
Complement System
Cascade of plasma proteins enhancing pathogen clearance and inflammation.
Overview
The complement system consists of >30 plasma proteins activated through three pathways: classical (antibody-mediated), lectin (mannose-binding), and alternative (spontaneous hydrolysis). All converge at C3 convertase formation, leading to opsonization (C3b), inflammation (C3a, C5a), and membrane attack complex (MAC) formation.
Cellular Location
Blood plasma, tissue fluids
Clinical Significance
Essential for innate immunity; complement inhibitors (eculizumab) treat PNH and aHUS.