6- Complement System

Question 1

What molecules are necessary for the initiation of the classical pathway of the complement system?

Answer 1

Antibody and C1q

Question 2

What molecules are necessary for the initiation of the lectin pathway of the complement system?

Answer 2

MBL
Manose-binding lectin

Question 3

What molecules are necessary for the initiation of the alternative pathway of the complement system?

Answer 3

P and D

Question 4

Describe the classical pathway of complement system

Answer 4

• start with antibody and C1q
• C1rs binds, then C4 binds
• C2 binds to C4
• C2 causes C3b to opsonize the pathogen and mark it for destruction
• then barrel formation of proteins around the pathogen and punches holes in pathogen

Question 5

Describe the lectin pathway of the complement system

Answer 5

• Starting with MBL, MASP-2 binds and is initiated
• the rest of the pathway is the same as classical

Question 6

Which of the three complement pathways is in adaptive immunity?

Answer 6

Classical pathway

Question 7

Describe the classical pathway of the complement system

Answer 7

• initiated when a complement fixing antibody (IgM, IgG) binds the antigen
• Binding site for the complement protein on Fc portion of the antibody ‘opens up’ when the antibody is bound to antigen

Question 8

Describe some of the components of the MB-Lectin Pathway

Answer 8

• initiated by the soluble pattern recognition molecules (PRR) that bind to carbohydrates on the microbe surfaces
• this activates enzymes that activate the complement
• part of innate immunity, adaptive is not required to initiate this pathway

Question 9

Which immunoglobulin is more efficient at activating the classical pathway of complement compared to IgG?

Answer 9

IgM