Molecular Defences – Complement

Question 1

what are the roles of the complement system

Answer 1

aid elimination of microbes by: opsoniation of pathogens, inflammation, lysis of microbes
eliminate apoptotic cells/debris, promote clearance of antigen:antibody complexes
promote B cell activation

Question 2

what are the three pathways of complement system

Answer 2

classical pathway
alternative pathway
mannose lectin pathway

Question 3

downstream consequence of all complement pathways result in:

Answer 3

1. Generation of C3 convertase, cleaves C3 to C3a and C3b

2. Generation of C5 convertase, cleaves C5 to C5a and C5b

Question 4

regardless of the trigger of initiation pathway you take what happens in the complement pathway

Answer 4

series of proteolytic cleavages= generation of C3 convertase -> into C3a and C3b
ultimately forming C5 convertase -> into C5a and C5b then get final steps of complement cascade

Question 5

how is complement activated when the microbe is new/no antibodies to it yet

Answer 5

activated by alternative pathway.

spontaneous cleavage of C3 (occurs in plasma all the time) to C3a and C3b which exposes