What are the 3 different complement pathways?
Complement can be activated through three pathways: classical, lectin, and alternative. The classical pathway is activated when C1q binds to antibody attached to antigen, activating C1r and C1s, which cleave C4 and C2.
What does the complement pathway do?
The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen’s cell membrane.
Where do the complement pathways converge?
All three pathways of complement activation converge at the formation of the C3 and C5 convertases, the latter of which cleaves C5. Cleavage of C5 produces the anaphylatoxin C5a, and a larger C5b fragment that initiates the non-enzymatic terminal pathway of complement (Figure 4).
What are the three most important products of the complement system?
Activated complement generates three major types of effectors: (1) anaphylatoxins (C3a and C5a), which are potent proinflammatory molecules that attract and activate leukocytes through interaction with their cognate G-protein–coupled receptors, C3a receptor (C3aR) and C5a receptor (C5aR); (2) opsonins (C3b, iC3b, and …
What triggers the classical complement pathway?
The classical pathway is normally triggered by antigen–antibody complexes that bind the C1 complex (C1q, C1r, C1s) through the C1q component. This activates C1s, which is then able to cleave the C4 complement protein into C4a and C4b. C4b attaches to its target surface via its exposed metastable thioester binding site.
What are the three functions of complement?
At the basic level the broad functions of the complement system can be split into three areas: (1) the activation of inflammation; (2) the opsonization (labeling) of pathogens and cells for clearance/destruction; (3) the direct killing of target cells/microbes by lysis.
How does complement help fight infections?
Complement works with the immune system Proteins of the complement system react with each other to bind pathogens and trigger an inflammatory cascade response to fight infection. Many complement proteins are proteases that are activated by proteolytic cleavage. These proteins are called zymogens.
Which type of antibody is most effective in activating complement?
IgM is specialized to activate complement efficiently upon binding antigen. IgG antibodies are usually of higher affinity and are found in blood and in extracellular fluid, where they can neutralize toxins, viruses, and bacteria, opsonize them for phagocytosis, and activate the complement system.
What are the 3 functions of the complement system?
What are two protective outcomes of complement activation?
Although each complement activation pathway is initiated in a different way, they all provide the same protective outcomes: opsonization, inflammation, chemotaxis, and cytolysis.
What activates the complement pathway?
This pathway is activated by the binding of mannose-binding lectin (MBL) to mannose residues on the pathogen surface. This in turn activates the MBL-associated serine proteases, MASP-1 and MASP-2, which activate C4 and C2, to form the C3 convertase, C4b2a.
What are the three pathways of complement activation?
Complement activation takes place through any of the following three pathways: 1. The classical pathway The classical pathway is a chain of events in which complement components react in specific sequences as a cascade resulting in cell lysis.
Which is the primary function of the complement system?
The primary function of the complement system is to bind and neutralize any foreign substance that activates it. Another function of the complement system is to enhance phagocytosis. 3.1 1. The classical pathway 3.2 2. The alternative pathway
Where does the lectin complement pathway take place?
The lectin complement pathway is initiated by microorganism-bound MBL as it associates with two human MBL-associated serine proteases (MASP-1 and -2) that cleave and activate C4 and C2.
How are serine proteases associated with the complement system?
Two other molecules called MBL-associated serine proteases 1 and 2 (MASP-1 and MASP-2) are associated with the MBL activation of complement system. MBL and MBL-associated serine proteases are believed to act as C1q, C1r, and C1s of the classic complement pathway.