Complement

Question 1

3 Pathways

Answer 1

Classic - Ab mediated, IgG or IgM
Alternative - microbe surface molecules like endotoxin
Lectin pathway - lectin is a protein that binds sugars. Mannose or other sugars on microbe surface

Question 2

C3b

Answer 2

Opsonization, also helps clear ICs

Question 3

C3a, C4a, C5a

Answer 3

Anaphylaxis. Treat with epinephrine

Question 4

C5a

Answer 4

Nphil chemotaxis (along with IL-8 and LTE-B4)

Question 5

C5b-9

Answer 5

Cytolysis by MAC

Question 6

2 Opsonins

Answer 6

C3b and IgG

Question 7

2 Inhibitors

Answer 7

C1 esterase (prevents Classic pathway activation) and Decay-Accelerating Factor (DAF aka CD55)

Question 8

C1 Esterase Inhibitor Deficiency

Answer 8

Causes hereditary angioedema because elevated bradykinin, so ACE INHIBITORS CONTRAINDICATED

Question 9

C3 Deficiency

Answer 9

Increases risk of severe, recurrent pyogenic sinus and respiratory tract infections (esp. by S. pneumo and H. influenzae), and increased susceptibility to Type III Hypersens Reactions

Question 10

C5-9 Deficiencies

Answer 10

Can’t make MAC (terminal complement goal), increased susceptibility to recurrent Neisseria bacteremia

Question 11

DAF (GPI-anchored enzyme) deficiency

Answer 11

Causes complement mediated lysis of RBCs and PNH