Complement cascade

Definition

The complement cascade is a series of protein activations in the blood that enhances immune responses by promoting inflammation, phagocytosis, and cell lysis. It is a crucial part of the innate immune system and complements the actions of antibodies in adaptive immunity.

5 Must Know Facts For Your Next Test

1. The complement cascade involves three pathways: classical, lectin, and alternative.
2. Activation of the complement system results in the formation of the Membrane Attack Complex (MAC) which can lyse pathogens.
3. C3 convertase is a key enzyme that cleaves C3 into C3a and C3b, crucial steps in all pathways.
4. The classical pathway is activated by antigen-antibody complexes (IgM or IgG).
5. Regulatory proteins such as Factor H and I prevent damage to host cells by inhibiting complement activation.

Related terms

Antigen-Antibody Complex:

A combination formed when an antibody binds to an antigen.

Phagocytosis:

The process by which cells engulf and digest particles or pathogens.

Membrane Attack Complex (MAC): A structure formed on pathogen surfaces leading to cell lysis.