Membrane attack complex (MAC)

Definition

The membrane attack complex (MAC) is a structure formed on the surface of pathogen cell membranes by the complement system, leading to cell lysis and death. It is a critical component in the immune system's defense against bacterial infections.

5 Must Know Facts For Your Next Test

1. The MAC is primarily composed of complement proteins C5b, C6, C7, C8, and multiple units of C9.
2. Formation of the MAC is part of the terminal pathway of the complement cascade.
3. MAC creates pores in the target cell membrane, leading to loss of cellular contents and eventual cell death.
4. Deficiencies in MAC components can lead to increased susceptibility to Neisseria infections.
5. MAC formation is a non-specific defense mechanism that targets a broad range of pathogens.

Review Questions

• What are the main components that form the membrane attack complex?
• How does the MAC contribute to pathogen destruction?
• Why might someone with a deficiency in MAC components be more susceptible to certain infections?

Related terms

Complement System: A group of blood proteins that help antibodies and phagocytic cells clear pathogens from an organism.

Neisseria: A genus of bacteria that includes species responsible for diseases such as gonorrhea and meningitis.

Cell Lysis: The breaking down or destruction of a cell membrane, resulting in the release of its contents.