Question: How Does The Complement System Work?

What is the role of the complement system?

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..

How does the complement system kill bacteria?

Complement is a complex protein network of plasma, and an integral part of the innate immune system. Complement activation results in the rapid clearance of bacteria by immune cells, and direct bacterial killing via large pore-forming complexes.

How do you remember complement pathways?

Mnemonic for Complement system:Classical pathway: Complex (Immune complex) activated; C1 + C4 – C2 = C3.Mannose binding lectin (MBL) pathway: Microbe mannose activated.Alternative pathway: Alien particles (like microbe or tumor cells) activated; Factors mediated.

What triggers complement system?

The classical complement pathway typically requires antigen—antibody complexes (immune complexes) for activation (specific immune response), whereas the alternative pathway can be activated by C3 hydrolysis, foreign material, pathogens, or damaged cells.

How does complement cause inflammation?

Activation of inflammation – Several peptides produced by proteolytic cleavage of complement proteins bind to vascular endothelial cells and lymphocytes. These cells then produce cytokines which stimulate inflammation and enhances responses to foreign antigens.

What are the 3 different complement pathways?

There are three pathways of complement activation: the classical pathway, which is triggered directly by pathogen or indirectly by antibody binding to the pathogen surface; the MB-lectin pathway; and the alternative pathway, which also provides an amplification loop for the other two pathways.

What is the difference between classical and alternative pathway?

The main difference between classical and alternative pathway is that the initiation of alternative pathways is not dependent on the presence of immune complexes. The lectin pathway is activated following the recognition and binding of pathogen-associated molecular patterns (PAMPs) by mannose-binding lectin (MBL) [27].

What happens during an inflammatory response?

The inflammatory response (inflammation) occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause. The damaged cells release chemicals including histamine, bradykinin, and prostaglandins. These chemicals cause blood vessels to leak fluid into the tissues, causing swelling.

How is the complement system activated?

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 is blood complement?

A complement test is a blood test that measures the activity of a group of proteins in the bloodstream. These proteins make up the complement system, which is one part of the immune system. The complement system helps antibodies fight off infections and destroy substances that are foreign to the body.

What triggers the alternative complement pathway?

The alternative pathway is one of three complement pathways that opsonize and kill pathogens. The pathway is triggered when the C3b protein directly binds a microbe. It can also be triggered by foreign materials and damaged tissues.

What is the outcome when the complement cascade is activated?

What are the 3 major outcomes of the complement cascade? … This pathway is triggered by complement factor C1 binding to antibodies bound to the surface of a pathogen. Antibody binding activates C1, causing it to cleave C2 (into C2a and C2b) and C4 (into C4a and C4b).

How does the complement system fight infection?

Complement protects against infection in three ways. Firstly, it activates a large number of complement proteins that bind to pathogens so that they can be engulfed by phagocytes. Second, fragments of complement proteins can act as chemoattractants to recruit phagocytes.

What are the four major functions of the complement system?

The complement system has four major function, including lysis of infectious organisms, activation of inflammation, opsonization and immune clearance. There are three different complement pathways, the classical complement pathway, the alternative complement pathway, and the mannose-binding lectin pathway.

What are the 3 outcomes of complement activation?

Its activation results in three major potential outcomes for microbes: cell lysis upon assembly and insertion of the terminal membrane attack complex (MAC), complement mediated opsonization, and the release of anaphylatoxins that enhance local inflammation.

What are the components of complement system?

Classical Pathway This pathway involves complement components C1, C2 and C4. The pathway is triggered by antibody-antigen complexes binding to C1, which itself has three subcomponents C1q, C1r and C1s.

Can complement kill viruses?

Being a major first line of immune defense, the complement system keeps a constant vigil against viruses. Its ability to recognize large panoply of viruses and virus-infected cells, and trigger the effector pathways, results in neutralization of viruses and killing of the infected cells.

Which complement protein is involved in inflammation?

Complement anaphylatoxins C3a, C4a, and C5a are potent inflammatory mediators, and C5b initiates the formation of C5b-9 terminal complement complex, which is incorporated into bacterial cell walls and induces the lysis of pathogens, in particular gram-negative Neisseria strains.