Complement Pathways Flashcards
What are complements?
Circulating and cell membrane proteins that form part of the innate immune system
What is the function of complement proteins?
Help the innate system
Promote inflammatory and immune responses
What are the 3 complement activation pathways?
- Classical
- Lectin
- Alternative
Why are there 3 pathways?
Redundancy in case 1 fails
How does the classical pathway act?
Antigen-antibody complexes —> complement activation
What are the 3 consequences of complement activation?
- Inflammatory cell recruitment
- Opsonization
- Pathogen killing
How is the classical complement pathway activated?
- C1 (complement component) binds to antigen-antibody complex via its C1q recognition region
How is the lectin pathway activated?
Mannan-binding lectin (MLB) binds to terminal polysaccharide on surface of microbe
-Not found on mammalian cell surfaces
How is the alternative pathway activated?
Deposition of complement component C3b on pathogen surface
At which complement component do the 3 different pathways converge?
C3
What is the relationship between the complement and immune system?
Bridge between the adaptive and immune system
Classical complement responds to the adaptive immune system (Ig production —> antigen-antibody complexes)
- Effector mechanism
What antibodies are involved in the classical pathway?
IgM or IgG
- Bind with antigen —> antibody-antigen complex
- Complex binds to C1q (subunit of C1)
