6: Complement Flashcards

1
Q

Two other systems that the complement works in cooperation with

A
  1. Blood coagulation pathways

2. Kinin-kallikrein system

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2
Q

Alternative C3 and C5 convertases

A

C3 convertase: C3bBb

C5 convertase: C3bBbC3b

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3
Q

Three extra proteins in alternative pathway

A

Properdin, factor B, factor D

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4
Q

Factor B (Bb)

A

Active enzyme of C3 and C5 convertases

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5
Q

Factor D

A

Cleaves factor B when bound to C3b

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6
Q

Properdin

A

Stabilizes alternative C3 convertase on microbe surfaces

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7
Q

What protein in alternative pathway is most abundant in serum

A

C3

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8
Q

Classical and lectin C3 and C5 convertases

A

C3 convertase: C4bC2a

C5 convertase: C4bC2aC3b

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9
Q

Four proteins involved in classical pathway

A

C1, C2a, C4a, C4b

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10
Q

C1: describe structure

A

C1q + tetramer of C1r (2) + C1s (2)

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11
Q

C1 function

A

Initiates classical pathway by binding IgM or IgG on Ag

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12
Q

C1q function

A

Binds Fc portion of Ab with 6 identical subunit arms

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13
Q

C1r function

A

Cleaves C1s to activate it

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14
Q

C1s function

A

Cleaves C4 and C2

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15
Q

Most abundant classical pathway protein in serum

A

C4

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16
Q

What initiates the lectin pathway

A

MBL binding bacterial surface -> activates MASPs

17
Q

Which MASP cleaves C4 and C3?

A

MASP2

18
Q

MASP structure

A

MASP1, 2, and 3 all form a complex together

19
Q

C1-INH function

A

Irreversibly inactivates C1r, C1s, and MASPs

20
Q

Side affect of C1-INH

A

Inhibits kallikrein-Kirin and coagulation cascades

21
Q

What causes swelling in hereditary angioedema?

A

Bradykinin, cleaved by kininongen when C1-INH isn’t present to inhibit kallikrein activating kininogen

22
Q

Factor I function

A

Inactivates C3b and C4b

23
Q

Four cofactors that can work with Factor I

A

MCP, CR1, factor H, C4BP

24
Q

Three proteins that destabilize CP/LP C3 convertases

A

DAF, CR1, C4BP

25
Q

Three proteins that destabilize AP C3 convertases

A

DAF, CR1, factor H

26
Q

Three proteins that inhibit MAC formation

A

CD59, vitronectin, S protein

27
Q

What does a deficiency in C1, C2, or C4 cause?

A

Immune complex disease

28
Q

What does a deficiency in C3 or factor I cause?

A

Susceptibility to capsulated bacteria

29
Q

What does a deficiency in MAC proteins cause

A

Susceptibility to Neisseria

30
Q

What does a deficiency in Factor D or properdin cause?

A

Susceptibility to capsulated bacteria + Neisseria

31
Q

What does a deficiency in DAF and CD59 cause?

A

Auto-immune like conditions (ex: PNH)

32
Q

What does a deficiency in C1-INh cause?

A

Hereditary angioedema (HAE)

33
Q

Lab test involved in testing complement

A

Ability of pt’s serum to lyse sheep RBCs

34
Q

CH50 and AH50 test results in complement testing

A

abnormal CH50 -> defect in CP
Abnormal APH50 -> defect in AP
Abnormal both -> defect in MAC or C3

35
Q

Symptoms of HAE

A

Edema in various parts of the body, abdominal pain, nausea, vomiting, swelling of airway can be fatal

36
Q

Triad of features in paroxysmal nocturnal hemoglobinuria (PNH)

A

Hemolysis, thrombosis, anemia

37
Q

What causes PNH?

A

Deficiency in GPI (DAF, CD59) -> Failure to regulate MAC formation

38
Q

What is the sign of poor prognosis in SLE patients?

A

Kidney involvement

39
Q

Two major causes of glomerular disorders

A
  1. Deposition of immune complexes -> CP activation

2. Abs binding directly to kidney self-Ags