Complement proteins

Definition

Complement proteins are a group of serum proteins that play a crucial role in the immune response by enhancing the ability to clear pathogens and damaged cells. They are part of the innate immune system and facilitate the detection and elimination of antigen-antibody complexes.

5 Must Know Facts For Your Next Test

1. Complement proteins can be activated through three pathways: classical, lectin, and alternative.
2. They form membrane attack complexes (MAC) that create pores in pathogen membranes, leading to cell lysis.
3. C3 is a central component in all three activation pathways and its cleavage is crucial for complement cascade progression.
4. Complement proteins enhance phagocytosis through opsonization, marking pathogens for destruction by phagocytes.
5. Regulatory proteins control complement activity to prevent damage to host tissues.

Review Questions

• What are the three pathways through which complement proteins can be activated?
• How do complement proteins contribute to the formation of membrane attack complexes (MAC)?
• What role does C3 play in the complement system?

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 membranes that leads to cell lysis.

Classical Pathway:

One of the three pathways for complement activation initiated by antigen-antibody complexes.