Abstract
The complement system (CS) is part of the human immune system, consisting of more than 30 proteins that play a vital role in the protection against various pathogens and diseases, including viral diseases. Activated via three pathways, the classical pathway (CP), the lectin pathway (LP), and the alternative pathway (AP), the complement system leads to the formation of a membrane attack complex (MAC) that disrupts the membrane of target cells, leading to cell lysis and death. Due to the increasing number of reports on its role in viral diseases, which may have implications for research on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), this review aims to highlight significant progress in understanding and defining the role of the complement system in four groups of diseases of viral etiology: (1) respiratory diseases; (2) acute liver failure (ALF); (3) disseminated intravascular coagulation (DIC); and (4) vector-borne diseases (VBDs). Some of these diseases already present a serious global health problem, while others are a matter of concern and require the collaboration of relevant national services and scientists with the World Health Organization (WHO) to avoid their spread.
Highlights
The complement system is a part of the immune system and plays the role of a functional bridge between innate and adaptive immune responses that allows an integrated host defense against pathogens [9]
When only OmCI was used, no decrease in virus titer was observed in lung tissue [98]. These results indicate that the C5a-C5aR1 axis plays an important role in the occurrence of Acute Lung Injury (ALI) induced by influenza virus infection, and that the use of anti-C5aR1 antibodies can suppress the hyperactive immune response induced by viral infection and effectively inhibit viral replication in the lung, thereby attenuating inflammatory responses and reducing lung injury in influenza [97,98]
The complement system is a part of the immune system that serves as a functional bridge between innate and adaptive immune responses
Summary
The complement system (CS) plays a key role in the defense against pathogens as part of the human immune system [1,2]. The molecules of C1s) binds to the Fc region of complement‐fixing antibodies (generally IgG1 larger fragments combine to form the C4bC2a complex on the pathogen surface which and IgM) attached to pathogenic surfaces and pathogen‐infected cells This results in the leads to the cleavage of C3 into anaphylatoxin C3a and opsonin C3b. The lectin complement system pathway is similar ments combine to form the C4bC2a complex on the pathogen surface which leads to the to the classical pathway, but is independent of immunoglobulins. It does not recognize cleavage of C3 into anaphylatoxin C3a and opsonin C3b. The complement system, with its ability to form channels in the cell membrane, induce phagocytosis, and cause mast cell degranulation, is a dangerous weapon, and without constant supervision by the various mechanisms regulating its activity (Table 1), it could lead to cell and tissue damage in our body
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