positive regulation of activation of membrane attack complex

Definition

Target type: biologicalprocess

Any process that activates, maintains or increases the frequency, rate or extent of the activation of the membrane attack complex components of the complement cascade. [GOC:hjd]

The positive regulation of activation of the membrane attack complex (MAC) is a complex and tightly regulated process that plays a crucial role in the innate immune system. It involves a series of steps that ultimately lead to the formation of the MAC, a pore-forming complex that can lyse target cells. Here's a detailed description of the biological process:

1. **Initiation:** The process begins with the recognition of a pathogen or an altered self-cell by immune cells. This recognition is often mediated by pattern recognition receptors (PRRs) that bind to pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs).

2. **Complement Activation:** Recognition of the target cell activates the complement system, a cascade of proteins in the blood that plays a critical role in innate immunity. There are three major pathways of complement activation: the classical pathway, the alternative pathway, and the lectin pathway. Each pathway utilizes different initiation mechanisms but ultimately converge on the formation of the C3 convertase, an enzyme responsible for cleaving C3, a central component of the complement system.

3. **Formation of the C5 convertase:** The C3 convertase cleaves C3 into C3a and C3b. C3b then binds to the surface of the target cell. This binding event facilitates the formation of the C5 convertase, another critical enzyme in the complement cascade.

4. **C5 Cleavage and MAC Assembly:** The C5 convertase cleaves C5 into C5a and C5b. C5b initiates the assembly of the MAC. C6, C7, and C8 join C5b, forming a complex that binds to the cell membrane. This complex then recruits multiple molecules of C9, which polymerize into a pore-like structure, the MAC.

5. **MAC Formation and Lysis:** The assembled MAC inserts itself into the cell membrane, creating a transmembrane channel. This channel allows for the influx of water and ions into the target cell, disrupting its osmotic balance and leading to cell lysis.

6. **Regulation:** The activation of the MAC is tightly regulated to prevent excessive cell lysis and collateral damage to healthy cells. Several regulatory proteins are involved in this process, including C1 inhibitor (C1INH), Factor H, and Factor I. These proteins inhibit the activation of the complement cascade and prevent the formation of the MAC.

**In Summary:** The positive regulation of activation of the membrane attack complex is a crucial process in the innate immune system that involves a cascade of complement proteins, leading to the formation of a pore-forming structure that lyses target cells. This process is tightly regulated to prevent excessive cell damage and ensure the proper functioning of the immune system.'
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Proteins (1)

Compounds (1)