Three pathways that trigger complement activation include:
- Alternative pathway
- Classical pathway
- Lectin pathway

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Pathways Triggering Complement Activation

A cascade in which complement precursors become functional. This process can be triggered in three different pathways.

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Features of the complement system include:
- Complement proteins
- Complement activation
- Opsonization
- Membrane attack complex

Features of the Complement System

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Plasma protein mediators of the complement system. They normally circulate as precursor proteins in blood, and are considered components of innate immunity due to their constant presence in the blood and thus capable of quick activation. In alternative pathways, these proteins target invaders nonspecifically. 

Complement Proteins

Complement Activation

A complex comprised of complement proteins C6, C7, C8, and C9, which when assembled causes C9 to polymerize into pores in gram-negative bacterial membranes. These pores let in molecules such as water and ions that accumulate within the bacterial cells and cause cell lysis and death. MAC is not effective for the destruction of gram-positive bacteria, hence a more heavy reliance on opsonization.

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