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
First complement component to bind in the classical pathway
C1
26
Subunits of C1
C1q, C1r, C1s
27
Stabilizing factor for C1
Calcium
28
Components of the alternative pathway
C3, Factor B, Factor D, Properdin
29
Triggering substances for the alternative pathway
Pathogens (bacteria, fungi, viruses, parasites), non-pathogens (immune complexes, RBCs, polymers)
30
First step in the alternative pathway
Conversion of C3
31
Factor B role in the alternative pathway
Analogous to C2 in the classical pathway
32
Plasma protein that cleaves Factor B after binding to C3b in the alternative pathway
Factor D
33
Cleavage products of Factor B by Factor D
Ba and Bb
34
Alternative pathway C3 convertase
C3bBb
35
Alternative pathway C5 convertase
C3bBb3bP
36
Similarity between alternative and classical pathways
Identical after C5 cleavage
37
Key Protein in MBL Pathway
Lectin (binds to carbohydrates)
38
MBL Function
Binds to mannose on bacterial cells
39
MBL Production Site
Liver (during acute-phase inflammatory reactions)
40
Enzymes Binding MBL
MASP-1, MASP-2
41
Function of MASP-1 and MASP-2
Similar to C1 activity in the classical pathway
42
Recognition Unit
MBP, MASP-1
43
Role of MASP-1
Cleaves C3
44
Role of MASP-2
Cleaves C4 and C2
45
C3 Convertase in MBL Pathway
C4b2a
46
C5 Convertase in MBL Pathway
C4b2a3b
47
Importance of MBL Pathway
Innate host defense in early childhood
48
Structural Similarity of MBL Complex
Resembles C1q of the classical pathway
49
Activation Triggers of MBL Pathway
D-mannose, GlcNAc, microbial polysaccharides
50
Prevents activation of complement proteins
Plasma complement regulation
51
Dissociates C1r and C1s from C1q
C1 Inhibitor (C1 Inh)
52
Cleaves C3b and C4b
Factor I
53
Inactivates C3b and prevents Factor B binding in the alternative pathway
Factor H
54
Cofactor with Factor I to inactivate C4b
C4 Binding Protein
55
Prevents attachment of the C5b67 complex to cell membranes
S Protein (Vitronectin)
56
Accelerates dissociation of C3 convertase
Decay Accelerating Factor (DAF)
57
Inhibitors of Membrane Attack Complex (MAC)
HRF (Homologous Restriction Factor) and MIRL (CD59)
58
Mediates immune complex transport and is a cofactor for Factor I
CR1 (CD35)
59
B-cell co-receptor for antigens with CD19
CR2 (CD21)
60
Enhances adhesion and activity of phagocytic cells
CR3 (CD11b/CD18) and CR4 (CD11c/CD18)
61
Prevents insertion of C9 into the cell membrane
MIRL (CD59)
62
Cofactor for Factor I cleavage of C3b and C4b
MCP (CD46)
63
Assay for hemolysis via classical pathway
CH50 assay (using sensitized sheep RBC)
64
Assay for hemolysis via alternative pathway
AH50 assay (using magnesium chloride, ethylene glycol tetraacetic acid)
65
Test for concentration of complement component C3
Radial Immunodiffusion (RID)
66
Decreased complement components is due to
Consumption (autoimmune) or genetic defect
67
Detects complement-fixing antibodies after antigen-antibody binding
"Complement fixation test"
68
Systems involved in complement fixation
Test/Bacteriolytic System & Indicator/Hemolytic System
69
Complement fixation test reporting
Positive: no hemolysis; Negative: hemolysis