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IMMUNOSEROLOGY > Complement system > Flashcards

Complement system Flashcards

1
Q

Function of the complement system

A

Cytolytic destruction of cellular antigens by specific antibody

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2
Q

Chemotaxins in complement system

A

C5a, C5b, C6, C7

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3
Q

Immune adherence mediator

A

C3b

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4
Q

Kinin activator in complement system

A

C2b

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5
Q

Anaphylotoxins in complement system

A

C3a, C4a, C5a (most potent)

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6
Q

Opsonins in complement system

A

C3b, C4b, C5b

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7
Q

Complement fragments involved in virus neutralization

A

C4b, C1

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8
Q

Number of IgM molecules required to activate complement

A

1 molecule

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9
Q

Number of IgG molecules required to activate complement

A

2 molecules

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10
Q

Complement fragment exception where ‘a’ is larger than ‘b’

A

C2a is larger than C2b

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11
Q

Most abundant complement protein

A

C3

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12
Q

Most commonly measured complement protein fragment

A

C3b

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13
Q

Three major pathways of complement activation

A

Classical, Alternative, Lectin

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14
Q

Pathway activated by antibody bound to antigen

A

Classical pathway

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15
Q

Pathway activated on microbial cell surfaces without antibody

A

Alternative pathway

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16
Q

Pathway activated by plasma lectin binding mannose on microbes

A

Lectin pathway

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17
Q

Recognition unit in the classical pathway

A

C1

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18
Q

Activation unit in the classical pathway

A

C4, C2, C3

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19
Q

Membrane attack complex (MAC) components

A

C5, C6, C7, C8, C9

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20
Q

Classical pathway C3 convertase

A

C4bC2a

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21
Q

Classical pathway C5 convertase

A

C4b2a3b

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22
Q

Subunit of C1 that binds to antibody Fc region

A

C1q

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23
Q

Role of C1r and C1s subunits

A

Generate enzyme activity to start cascade

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24
Q

Enzyme classification of C1r and C1s

A

Serine protease proenzymes (zymogens)

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25
Q

First complement component to bind in the classical pathway

A

C1

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26
Q

Subunits of C1

A

C1q, C1r, C1s

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27
Q

Stabilizing factor for C1

A

Calcium

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28
Q

Components of the alternative pathway

A

C3, Factor B, Factor D, Properdin

29
Q

Triggering substances for the alternative pathway

A

Pathogens (bacteria, fungi, viruses, parasites), non-pathogens (immune complexes, RBCs, polymers)

30
Q

First step in the alternative pathway

A

Conversion of C3

31
Q

Factor B role in the alternative pathway

A

Analogous to C2 in the classical pathway

32
Q

Plasma protein that cleaves Factor B after binding to C3b in the alternative pathway

A

Factor D

33
Q

Cleavage products of Factor B by Factor D

A

Ba and Bb

34
Q

Alternative pathway C3 convertase

A

C3bBb

35
Q

Alternative pathway C5 convertase

A

C3bBb3bP

36
Q

Similarity between alternative and classical pathways

A

Identical after C5 cleavage

37
Q

Key Protein in MBL Pathway

A

Lectin (binds to carbohydrates)

38
Q

MBL Function

A

Binds to mannose on bacterial cells

39
Q

MBL Production Site

A

Liver (during acute-phase inflammatory reactions)

40
Q

Enzymes Binding MBL

A

MASP-1, MASP-2

41
Q

Function of MASP-1 and MASP-2

A

Similar to C1 activity in the classical pathway

42
Q

Recognition Unit

A

MBP, MASP-1

43
Q

Role of MASP-1

A

Cleaves C3

44
Q

Role of MASP-2

A

Cleaves C4 and C2

45
Q

C3 Convertase in MBL Pathway

A

C4b2a

46
Q

C5 Convertase in MBL Pathway

A

C4b2a3b

47
Q

Importance of MBL Pathway

A

Innate host defense in early childhood

48
Q

Structural Similarity of MBL Complex

A

Resembles C1q of the classical pathway

49
Q

Activation Triggers of MBL Pathway

A

D-mannose, GlcNAc, microbial polysaccharides

50
Q

Prevents activation of complement proteins

A

Plasma complement regulation

51
Q

Dissociates C1r and C1s from C1q

A

C1 Inhibitor (C1 Inh)

52
Q

Cleaves C3b and C4b

A

Factor I

53
Q

Inactivates C3b and prevents Factor B binding in the alternative pathway

A

Factor H

54
Q

Cofactor with Factor I to inactivate C4b

A

C4 Binding Protein

55
Q

Prevents attachment of the C5b67 complex to cell membranes

A

S Protein (Vitronectin)

56
Q

Accelerates dissociation of C3 convertase

A

Decay Accelerating Factor (DAF)

57
Q

Inhibitors of Membrane Attack Complex (MAC)

A

HRF (Homologous Restriction Factor) and MIRL (CD59)

58
Q

Mediates immune complex transport and is a cofactor for Factor I

A

CR1 (CD35)

59
Q

B-cell co-receptor for antigens with CD19

A

CR2 (CD21)

60
Q

Enhances adhesion and activity of phagocytic cells

A

CR3 (CD11b/CD18) and CR4 (CD11c/CD18)

61
Q

Prevents insertion of C9 into the cell membrane

A

MIRL (CD59)

62
Q

Cofactor for Factor I cleavage of C3b and C4b

A

MCP (CD46)

63
Q

Assay for hemolysis via classical pathway

A

CH50 assay (using sensitized sheep RBC)

64
Q

Assay for hemolysis via alternative pathway

A

AH50 assay (using magnesium chloride, ethylene glycol tetraacetic acid)

65
Q

Test for concentration of complement component C3

A

Radial Immunodiffusion (RID)

66
Q

Decreased complement components is due to

A

Consumption (autoimmune) or genetic defect

67
Q

Detects complement-fixing antibodies after antigen-antibody binding

A

“Complement fixation test”

68
Q

Systems involved in complement fixation

A

Test/Bacteriolytic System & Indicator/Hemolytic System

69
Q

Complement fixation test reporting

A

Positive: no hemolysis; Negative: hemolysis

IMMUNOSEROLOGY (22 decks)

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