Membranangriffskomplex

The Membranangriffskomplex, often abbreviated as MAC, is a crucial component of the complement system in immunology. This complex is a pore-forming structure responsible for the lysis of target cells, such as bacteria and other pathogens. It is the final stage in the complement cascade, a series of biochemical reactions that mark and destroy invaders.

The formation of the MAC begins when several complement proteins, specifically C5b, C6, C7, and C8, assemble on the surface of the target cell. This initial assembly then recruits multiple copies of the complement protein C9. These C9 molecules polymerize, creating a transmembrane channel. This channel disrupts the integrity of the target cell's membrane, leading to an influx of extracellular fluid and ions.

The osmotic imbalance caused by this influx results in the swelling and eventual bursting of the cell, a process known as cell lysis. The MAC is a highly effective mechanism for eliminating extracellular pathogens. Its formation is tightly regulated to prevent damage to host cells. Defects in MAC formation can impair the immune system's ability to fight certain bacterial infections.