What components make up the membrane attack complex of complement activation?

The membrane attack complex (MAC) is a critical component of the immune response, specifically in the complement system, which helps to eliminate pathogens. The correct answer includes the proteins C5, C6, C7, C8, and C9.

These components work together to form the MAC, which facilitates the lysis (destruction) of target cells, such as bacteria. The process begins when C5 is cleaved to generate C5b, which then associates with C6. This C5bC6 complex subsequently binds to C7, enabling the insertion of the complex into the target cell membrane. Once inserted, the complex recruits C8 and multiple C9 molecules to form a pore-like structure in the membrane of the target cell, ultimately leading to its lysis by creating an osmotic imbalance.

By contrast, while C3, C4, and C5 appear in various stages of complement activation, they are not part of the membrane attack complex itself. C3 is critical in the initial complement activation pathways, and C4 plays a role in the classical pathway, but they do not contribute directly to the formation of the MAC. Some of the other options, while listing various components, either lack some essential proteins or mix components