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Immunology > Complements > Flashcards

Complements Flashcards

1
Q

What are complements?

A
  • group of serum proteins in inactive form
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2
Q

Once a complement is activated what are its main roles?

A
  • lysis
  • opsonization
  • inflammation
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3
Q

List the 6 categories of complements.

A
  1. Initiators
  2. Enzymatic mediators
  3. Opsonins
  4. Inflammatory mediators (anaphylatoxins)
  5. Membrane attack proteins
  6. Complement receptors (macrophages)
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4
Q

What are the 3 major pathways of complement activation?

A
  • Classical
  • Lectin
  • Alternative
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5
Q

All three complement pathways converge in the generation of:
A. C3b
B. C5 convertase
C. C3 convertase
D. C4

A

C. C3 convertase

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6
Q

C3 convertase cleaves which enzyme?

A

C3
- cleaves into C3a and C3b

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7
Q

C4b2a makes up….
A. C3 convertase
B. C5 convertase
C. Factor B
D. MASPs

A

A. C3 convertase

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8
Q

When C3b is added to C3 convertase to make C4b2a3b, what is the result?

A

C5 convertase
- cleaves C5 to C5a and C5b

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9
Q

How does C3b protect the host?

A
  1. Opsonization
    - C3b binds to microbial surfaces to “tag” for recognition
  2. Antigen-antibody complexes
    - C3b attaches to Fc portion of antibodies for phagocytosis
  3. C5 convertase
    - C3b bind to complement proteins to form C5 convertase
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10
Q

The classical pathway activated by:

A

Antigen-antibody complexes
- only IgM and IgG

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11
Q

What is activated by binding to an antibody in the classical pathway, initiating the classical cascade?
A. C4
B. C1
C. C2

A

B. C1

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12
Q

C1 activation is followed by…..

A

cleavage of C4 and C2 into (C4a/C4b) (C2a/C2b)

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13
Q

C4b2a bound to the cell surface forms (____) and then cleaves C3 into (_____).

A

C3 convertase; C3a and C3b

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14
Q

C3b combines with (_____) to form (___) convertase.

A

C3 convertase (C4bC2a); C5 convertase (C4bC2aC3b)

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15
Q

C5 convertase cleaves which protein?

A

C5 protein

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16
Q

The lectin pathway is activated by:

A

mannose-binding lectins (MBLs)

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17
Q

What do lectins recognize?

A
  • carbohydrate components on microbes
18
Q

Lectins serve as docking sites for:
A. C1
B. C3b
C. MASPs
D. DAMPs

19
Q

MASPs initiate the lectin pathway and cleave (___) and (____) to form C3 convertase.

20
Q

How are MASPs activated?

A
  • MLB binding to microbial surfaces
21
Q

T/F. After C3 convertase is formed the lectin pathway uses the same downstream components as the classical pathway

22
Q

The alternative pathway is activated by?

23
Q

In the alternative pathway, what is C3 convertase and C5 convertase composed of?

A

C3 convertase = C3bBb
C5 convertase = C3bBbC3b

24
Q

In the alternative tickover pathway, small amounts of C3 are spontaneously cleaved to yield:

25
Q

Fluid C3 initiates or activates the alternative pathway?

26
Q

Factor B binds to C3b on the microbial surface and is cleaved by
A. Ba
B. Factor D
C. C3Bb

A

B. Factor D

27
Q

Cleaving of Factor B causes which protein to be released and bound to fluid C3?

28
Q

Fluid-phase C3 convertase is:

A

Fluid C3Bb

29
Q

C5 initiates the generation of the (____) complex.

30
Q

The MAC complex is a result of which proteins on target cell membranes?

A

C5b, C6, C7, C8 , C9

31
Q

What are the 3 complement receptors?

A
  • CR1
  • CR2
  • C3aR/C5aR
32
Q

CR1 receptor binds to (___) on leukocytes and erythrocytes.

33
Q

CR2 receptor binds to (____) on B-cells.

34
Q

C3aR/C5aR receptor binds to (____) and (____) on granulocytes.

35
Q

Which complements act as anaphylatoxins or inducers of inflammation?

A

C3a and C5a

36
Q

What bridges complements to effectors?

37
Q

How do complements enhance host defense against infections?

A
  1. MAC-induced cell death
  2. C3b mediated phagocytosis
  3. Inflammation via C3a+C5a
38
Q

Identify this pathway.

39
Q

Identify this pathway.

40
Q

Identify this pathway.

A

Alternative

Immunology (19 decks)

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