Complement

Question 1

What is the function of Factor D in the complement system?

Answer 1

Factor D cleaves and activates Factor B

Question 2

What bacterial component can activate the Alternate Pathway directly without the need for Antibody-antigen complexes?

Answer 2

LPS Capsular polysaccharide

Question 3

In what way are the classical and alternative pathways for complement activation identical?

Answer 3

Factors H and I cleave and inactivate C3b.

Question 4

Classical pathway differs from the alternate pathway of complement activation because…

Answer 4

Only the classical pathway requires antigen-antibody complexes to bind and activate C1q.

Question 5

What antibody isotypes are detectable in a complement fixation assay?

Answer 5

IgG and IgM

Question 6

Describe the defect(s) associated with C5 deficiency.

Answer 6

• high susceptibility to Neisseria infection

- inability to form the MAC attack complex via C5b

Question 7

What products of complement activation can cause mast cell degranulation?

Answer 7

C3a (active) and C5a

Question 8

What complement product can opsonize microbes to make them easier to be phagocytosed?

Answer 8

C3b (either inactive or active)

Question 9

What complement pathway may be activated in a fungal infection? How does it work?

Answer 9

Complement can be activated directly by mannose-binding-lectin (MBL) being bound to fungal cell walls.

Question 10

What complement factor directly activates complement when bound to bacterial polysaccharides?

Answer 10

Properdin