Complement Activation: Part II

Question 1

The lectin complement pathway is considered ____________, as lectins like _________ ________ ______ and ________, bind to the surfaces of microbes.

Answer 1

Independent

Mannose binding lectin and Ficolins

Question 2

True or False: Both C-reactive protein and mannose binding lectin are both examples of acute phase proteins, that will be found at low plasma concentrations unless an infection is occuring.

Answer 2

True

Question 3

Similarly to C1q, _______ ________ _____ has a similar structure, and can bind along the cell wall of the bacterium and fungi, as well as viral envelopes and some protozoa.

Answer 3

Mannose binding lectin

Question 4

Which of the following is not associated with the binding of MBL?

A) N-acetyl -D-glucosamine
B) L-fucose
C) L-glucose
D) D-mannose

Answer 4

C) L-glucose
MBL recognizes mannose, fucose, and N-acetylglucosamine

Question 5

What occurs following the binding of MBL to mannose, fucose, or N-acetylglucosamine (specific carbohydrate moieties) along a mircobial surface?

Answer 5

The activation of MASPs which cleaves C4, C2 and then C3, to form C5 convertase

Question 6

True or False: C1 is the most abundant complement protein in the all three pathways of the complement system.

Answer 6

False, it is C3

Question 7

In what complement system pathway will C3 be spontaneously cleaved and acitivated?

Answer 7

Alternative pathway

Question 8

What occurs following the binding of C3b to the surface of a pathogen with increased sialic acid?

Answer 8

The C3b protein will likely be degraded due to the association of sialic acid, leading to the binding of factors H and I

Question 9

Pneumocystis carinii is observed in diseased lung tissue. Following analysis, this bacerium has no sialic acid and only receptors that can be bound by MBL. What will this result in?

Answer 9

This bacterium can either be lysed directly through the activation of the lectin pathway via a MAC, or marked for phagocytosis as MBL can act as an opsonin

Question 10

Herpes virus type I (HSV-1) is shown as the pathogenic agent in your pathology report. Notably, this virus has a very minimal concentration of Factor H, and higher amounts of sialic acid, on its envelope. What effect will this have on the lectin pathway?

Answer 10

Lead to the likely degradation of C3b, as sialic acid promoties its binding to Factor H, and then Factor I for inactivaiton and elimination; only if C3b manages to bind to Factor B will it have a chance to lead to the formation of a MAC

Question 11

What factor is associated with the binding of C3b in the lectin pathway to prevent degradation of it along a microbial surface?

Answer 11

Factor B, which is cleaved by Factor D to form the alternative C3 convertase

Question 12

True or False: Due its stability, the alternative C3 convertase can cleave C3 protein more efficiently cleave C3 into C3a and C3b activating the process again.

Answer 12

False, alternative C3 convertase is unstable and must be bound to Properdin or Factor P

Question 13

What factor binds to C3b convertase C3bBb on microbial surfaces and protects it from inhibition from another plasma protein?

A) Factor I
B) Factor H
C) Factor P
D) Factor Q

Answer 13

C) Factor P

Question 14

The alternative C5 convertase complex is formed by the cleavage of _____ by _________ ___ _______.

Answer 14

C3

Alternative C3 convertase

Question 15

What is the name for the following complex, and what products will it form?

C3bBb

Answer 15

Alternative C3 convertase, forming C3a and C3b (of which only C3b will bind to the complex)

Question 16

What is the name of this complex, and what products will it form?

C3bBb3b

Answer 16

Alternative C5 convertase, and it will form C5a and C5b (of which C5b will bind to this complex)

Question 17

C5 convertase (C4b2a3b) is the product of what pathway(s)?

Answer 17

Classical and Lectin pathways

Question 18

C5 convertase (C3bBb3B) is the product of what pathway(s)?

Answer 18

Alternative pathway

Question 19

Describe the formation of the membrane attack complex, following the formation of C5 convertase?

Question 20

Which of the following will have a direct impact and inhibition in the formation of pore needed to lyse the micobial membrane?

A) CD55
B) Factor H
C) CD59
D) C1 inhibitor
E) Factor I

Answer 20

C) CD59

This protein, also known as Protectin, will bind to the C5b678 complex to prevent the binding of C9 proteins

Question 21

Which of the following will accelerate the degradation of C3bBb, and is independent of sialic acid concentrations?

A) CD55
B) Factor H
C) CD59
D) C1 inhibitor
E) Factor I

Answer 21

A) CD55
This protein is also known as Decay-accelerating factor

Question 22

What pathway(s) is/are associated with the C1 inhibitor?

Answer 22

Classical and Lectin pathways

Question 23

What effects to C3a and C5a have following their cleavage?

Answer 23

• Osmodysregulation and lysis of targeted cells
• Activating Mast cells to degranulate
• Increased production of CAM’s
• Leukocyte extravasation and chemotaxis

Question 24

What roles do C3b and iC3b have?

Answer 24

Opsonization, or the enhancement of phagocytosis by professional phagocytic cells