Fig. 2

Complement activation pathways [42, 48, 52]. The three complement activation pathways—the classical, lectin, and alternative pathways—eliminate or clear infection or damaged host cells. The classical pathway initiates complement activation through antibody binding to immune complexes. The lectin pathway is initiated when pattern-recognition molecules bind to certain molecular patterns presented on damaged, malignant or distressed self-tissue or on microbes. The alternative pathway acts as an amplification loop of the classical or lectin pathways. All three pathways converge to mediate cleavage of C3, leading to initiation of the terminal pathway and assembly of the MAC. The coagulation cascade can be activated via MASP-2 cleavage of prothrombin to thrombin and cleavage of Factor XII to XIIa. MAC membrane attack complex, MASP mannan-binding lectin-associated serine proteases, MBL mannose-binding lectin