Complement

Question 1

What is complement?

Answer 1

A system of interacting proteins that play a role in innate immunity and inflammation (p.199)

Question 2

What types of bacteria does the Membrane attack complex (MAC) of complement specifically protect against?

Answer 2

Gram negative bacteria (p.199)

Question 3

What immunoglobulins mediate activation of the classic pathway of complement?

Answer 3

IgG or IgM (pneumonic: GM makes classic cars) (p.199)

Question 4

What activates the alternative pathway of complement?

Answer 4

Microbe surface molecules (p.199)

Question 5

What activates the lectin pathway of complement activation?

Answer 5

Mannose or other sugars on the microbe surface (p.199)

Question 6

What are the three pathways of complement activation?

Answer 6

Classic, Alternative, Lectin pathways (p.199)

Question 7

What is the function of C3b?

Answer 7

Opsonization (p.199)

Question 8

What is the function of C3a and C5a together?

Answer 8

Anaphylaxis (p.199)

Question 9

What is the function of C5a individually?

Answer 9

Neutrophil chemotaxis (p.199)

Question 10

What complement factors are involved in cytolysis by MAC?

Answer 10

C5b- C9 (p.199)

Question 11

Name the two primary opsonins in bacterial defense.

Answer 11

C3b and IgG (p.199)

Question 12

Name another important function of C3b.

Answer 12

C3b helps clear immune complexes (p.199)

Question 13

What two factors inhibit complement activation on self cells (e.x. RBCs)?

Answer 13

Decay accelerating factor (DAF) and C1 esterase inhibitor (p.199)

Question 14

Describe the steps of the alternative pathway of complement activation.

Answer 14

Spontaneous and microbial surfaces act on C3. C3 –> C3b –> C3 Convertase –> C3a + C3b. C3b –> C5 convertase –> C5b –> MAC –> lysis, cytotoxicity (p.199)

Question 15

Describe the steps of the classic pathway of complement activation.

Answer 15

Antigen antibody complexes cause C1 to convert C2 –> C2a which when added to C4b becomes C3 convertase –> C3b + C3a. C3b –> C5 convertase –> C5b –> MAC –> lysis, cytotoxicity (p.199)

Question 16

Describe the steps of the alternative pathway of complement activation.

Answer 16

Microbial surfaces (ex. Mannose) turns a C1 like complex into C1. C1 converts C2 –> C2a which when added to C4b becomes C3 convertase –> C3b + C3a. C3b –> C5 convertase –> C5b –> MAC –> lysis, cytotoxicity (p.199)

Question 17

What are the clinical manifestations of a C1 esterase inhibitor deficiency?

Answer 17

Hereditary angioedema (p.200)

Question 18

What types of medications are contraindicated in a patient with a C1 esterase inhibitor deficiency?

Answer 18

ACE inhibitors (p.200)

Question 19

What are the clinical manifestations of a C3 deficiency?

Answer 19

Severe, recurrent pyogenic sinus and respiratory tract infections; increased susceptability to type III hypersensitivity reactions (p.200)

Question 20

What are the clinical manifestations of a C5-C9 deficiency?

Answer 20

Recurrent Neisseria bacteremia (p.200)

Question 21

What type of bacterial infection is most common in patients with a C5-C9 deficiency?

Answer 21

Neisseria bacteremia (p.200)

Question 22

What are the clinical manifestations of a DAF (GPI anchored enzyme) deficiency?

Answer 22

Complement mediated lysis of RBCs and paroxysmal nocturnal hemoglobinuria (PNH) (p.200)