Complement System

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41 Terms

1
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What is the complement system?

a group of serum proteins that interact to destroy invading microbes

2
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Where are most plasma complement proteins synthesized?

in the liver

3
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What is the most popular complement protein?

C3

4
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Why is C3 the most popular complement protein?

that's where all 3 pathways converge

5
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What do all cleavage steps in the alternate pathway do?

yield activation

6
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What is the most innate pathway?

the lectin pathway

7
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What are the early complement components?

C1, C2, C3, C4

8
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What are the half lives of complements?

short

9
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What are the duties of complements?

acts as opsonins

increase vascular permeability

recruit monocytes and neutrophils to antigens

trigger secretion of cytokines

10
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What are the three complement pathways?

classical

lectin

alternative

11
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What is the end product of the complement system?

lysis of the invading cell

12
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What is the characteristic of the classical pathway?

primarily antigens and antibodies

13
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What is the characteristic of the lectin pathway?

does not require antibodies

14
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What is the characteristic of the alternative pathway?

supports classical and lectin pathway

15
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What is the classical pathway

start with C1qrs

C4 and C2 come in

C4a and C2b leave

C4b2a is left (C3 convertase)

C3 comes in

C3 a leaves

C4b2a3b is left (C5 convertase)

C5 comes in

C5a leaves

C5b is left

C6, C7, C8, C9 comes in

these are polymerized and turns into C5b6789

16
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What is C5 covertase?

C4b2a3b

17
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What is the most efficient antibody in the classical pathway?

IgM

because of its multiply binding sites

18
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What are the substances that activate the classical pathway?

C-reactive protein

certain viruses

mycoplasmas

some protozoa

19
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What is the C1 complex?

C1q, C1r, C1s

calcium is required

20
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What is the recognition unit of the classical pathway?

C1q recognizes the Fc region

two globular heads of C1q needs to be bound

C1r and C1s are converted

C1r is activated

C1r cleaves and C1s is activated

C1 is activates and recognition ends

21
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When does activation begin in the classical pathway?

when C1s cleaves C4 to create C4b and C2 to create C2a

22
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What is the membrane attack complex of the classical pathway?

when C5b attaches to the membrane to create C5b6789

23
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What is the main point of the lection pathway?

a defense mechanism in infancy in between loss of maternal antibody and development of full antibody response

24
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What are the recognition molecules of the lectin pathway?

lectins, ficolins, CL-L1

25
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When does the lection pathway become identical to the classical pathway?

after the cleaving of C4 and C2

26
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How does the lectin pathway activate the coomplements?

by recognizing carbohydrates on microbial cell walls

27
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What is the mannan-binding lectin?

binds to mannose or related sugars in a calcium-dependent manner to initiate pathway

28
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What is the alternative pathway?

C3 is hydrolyzed and produces C3b

C3b binds to B

B is cleaved

Bb combines with C3b

More C3 is cleaved

C3bBbP is left

C5 is cleaved by C3bBbP

Identical to classical pathway after

29
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What is the C5 convertase in the alternative pathway?

C3bBbP

30
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What is the C1-INH serum protein?

dissociates C1r and C1s from C1q

31
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What are the system controls?

C1-INH, Factor I, Factor H, S protein

32
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What is factor I?

Cleaves C3b and C4b

33
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What is Factor H?

Cofactor with I to inactivate C3b; prevents binding of B to C3b

34
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What is the S protein?

Prevents attachment of C5b67 complex to cell membranes

35
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What are the manifestations of complement activation?

amplifies inflammatory response

destruction of antigen

facilitate B cell activation

36
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When can complement be harmful?

it is activated systemically on a large scale

it is activated by tissue necrosis

lysis of RBCs occurs

37
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What is the CH50 functional test?

measures the function of the complete classical pathway

38
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What if the results of a CH50 functional test is outside the normal range?

each complement level must be measured to look for hereditary or acquired deficiencies

39
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What are the immunological assays of individual components?

radial immunodiffusion (RID)

nephlometry

40
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What are the classical pathway assays?

hemolytic titration (CH50)

CH50 for lysis of liposomes

radial hemolysis

41
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What are the alternative pathway assays?

AH50

ELISA