Complement activation

Definition

Complement activation is a crucial part of the immune system that enhances the ability to clear pathogens and damaged cells from an organism. It involves a cascade of protein interactions leading to pathogen opsonization, inflammation, and cell lysis.

5 Must Know Facts For Your Next Test

1. Complement activation can be triggered through three pathways: classical, lectin, and alternative.
2. The classical pathway is initiated by antigen-antibody complexes.
3. The lectin pathway is activated by mannose-binding lectin binding to carbohydrates on pathogen surfaces.
4. The alternative pathway is spontaneously activated on microbial surfaces in the absence of antibodies.
5. Key components involved in complement activation include C3 convertase and membrane attack complex (MAC).

Review Questions

• What are the three pathways that trigger complement activation?
• Which pathway of complement activation involves antigen-antibody complexes?
• What is the role of C3 convertase in complement activation?

Related terms

Opsonization:

The process by which pathogens are marked for ingestion and destruction by phagocytes.

Membrane Attack Complex (MAC): A structure formed on the surface of pathogen cell membranes that leads to cell lysis.

Mannose-Binding Lectin (MBL): A protein that binds to carbohydrates on pathogen surfaces, initiating the lectin pathway of complement activation.