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Immuno Unit 3 Self > 1 Antibody Structure and Function > Flashcards

1 Antibody Structure and Function Flashcards

1
Q

T-F–antigen receptors expressed by adaptive cells recognize a small diversity of antigens?

A

False–large diversity

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2
Q

Does the innate or adaptive immune system use pattern recognition as the infection sensing system?

A

Innate–receptors are limited and have fixed specificities and recognize only a finite number of microbial products

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3
Q

What molecules within B cell receptor complexes mediate antigen recognition and cell activation?

A

antibody molecules

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4
Q

What component dictates the antigen specificity of the BCR?

A

membrane-bound forms of antibodies component –variable region is key to diversity

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5
Q

Does engagement of one BCR complex by antigen lead to activation and the generation of antibodies?

A

No-multiple complexes engaging signal transduction along with other signals

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6
Q

What is the antigen specificity of antibodies determined by in developing B cells?

A

Gene rearrangement

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7
Q

What stage of B cell development rearrange genes encoding antibody components?

A

B cell progenitors– [more about this is later lecture]

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8
Q

T-f–each B cell clone expresses an antibody with a unique antigen specificity?

A

True

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9
Q

Are there a few different B cell clones produced or many? Why?

A

Millions

-produce antibodies specific to virtually any antigen

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10
Q

coding sequences assembled by gene rearrangement make up what in the BCR complex?

A

antibody antigen binding sites

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11
Q

T-F—antibodies recognize a variety of molecule as antigens?

A

True—proteins, nucleic acids, carbs, lipids

[NOTE: BROAD SPECIFICITY INCREASES ABILITY TO DETECT AND COMBAT MICROBIAL INFECTIONS]

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12
Q

T-F—TCRs can recognize a variety of molecules as antigens?

A

False—only recognize peptide-MHC complexes as antigens

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13
Q

Engagement of the BCR by antigen and activation of B cell leads to the production of what?

A

soluble antibodies

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14
Q

What is the main role of B cells in immune response?

A

recognize and respond to antigen and produce soluble antibodies?

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15
Q

What is the role of antibodies?

A

seek out and bind to antigens which initiates pathways to remove bound material

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16
Q

T-F— costimulatory signals are not needed in B cell activation?

A

False

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17
Q

Activated B cells proliferate and differentiate into?

A

antibody secreting cells

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18
Q

How do soluble antibodies distribute throughout the body?

A

passage through bloodstream

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19
Q

Antibodies are what shaped molecules?

A

Y

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20
Q

What is the makeup of the main shape of the antibody?

A

2 identical heavy chains

2 identical light chains

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21
Q

What holds the molecules together between anybody chains?

A

disulfide bonds

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22
Q

What do covalently linked carbohydrate chains to heavy chains do?

A

maintain antibody structure and stability—can influence function of the molecule

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23
Q

What are the 2 distinct functional domains of antibodies?

A

variable[Fab] and constant[Fc]

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24
Q

How many variable regions are there in antibodies?

A

2

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25
Q

amino acids in V regions are encoded by ?

A

randomly joined gene segments

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26
Q

T-F–constant region formed by N termini of heavy chains?

A

False–C-termini

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27
Q

What dictates the mulimerization state, anatomic localization and effector function?

A

Constant region

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28
Q

What does Fab stand for?

A

fragment of antigen binding

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29
Q

What does Fc stand for?

A

fragment crystallizable—form crystals when stored at cold temperatures

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30
Q

T-F—at the gene level, V regions are encoded by portions of the heavy and light chain genes that are generated by gene rearrangement?

A

True

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31
Q

T-F—within the V region, the C-termini of the heavy and light chains form a composite surface that mediates antigen binding?

A

False—it is the n-termini

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32
Q

What are segments in V regions that are highly diverse in the A.A. content and mediate direct contact with antigens?

A

complementarity determining regions (CDRs)

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33
Q

How can the antigen affinity of V regions be increased?

A

somatic mutation

affinity maturation

34
Q

What alters DNA sequences encoding V regions, resulting in AA changes within the antigen binding pocket?

A

somatic hypermutation

35
Q

What selects for B cell clones expressing antibodies with high affinity for antigen due to somatic hypermutation?

A

affinity maturation

36
Q

What does high affinity for antigen increase?

A

stability and duration of antigen-antibody interactions

37
Q

What do C regions dictate?

A

tissue distribution
multimerization state
antibody effector function

38
Q

How are human antibodies classified?

A

based on constant regions

39
Q

Where are IgM mostly found?

A

blood

40
Q

What is the most abundant Ig in body?

A

IgG– distributes to blood and tissue

41
Q

Where is IgE mostly found?

A

little in blood mostly in tissues bound to mast cells

42
Q

Where is IgA mostly found?

A

some in blood, but mainly secreted across epithelial layers lining respiratory and digestive tracts

43
Q

What Ig is expressed by mature B cells, integrated into BCRs and secreted very little?

A

IgD

44
Q

What do naive B cells express?

A

IgM and IgD

45
Q

Antibody secreting cells express?

A

IgG, IgA or IgE

46
Q

Activated B cells with T cell help will do what to heavy chain?

A

will recombine DNA encoding the heavy chain

47
Q

T-F—generally, B cells that undergo class switching also undergo somatic hypermutation and affinity maturation

A

True

48
Q

What antibody is transferred across placenta?

A

IgG

49
Q

What Ig forms pentamer?

A

IgM

50
Q

What Ig forms dimers?

A

IgA

51
Q

Infants receive what Igs from mother?

A

IgA (breast) and IgG (placenta)

52
Q

What type of bonds holds together antibody dimers and pentamers? Where does the multimerization occurs?

A
  • cysteine bonds with the J chain help

- occurs during transit through ER and Golgi

53
Q

What are the 5 pathways antibodies promote clearance of microbes?

A
  • agglutination
  • neutralization
  • activation of complement cascades
  • Fc Receptor-mediated opsonophagocytosis
  • antibody-dependent cytotoxicity
54
Q

What traps microbes in a complex preventing cell-cell contact and colony formation/replication?

A

agglutination

55
Q

What blocks contacts with host molecules and cells impeding attachment or entry into cells?

A

agglutination

56
Q

Agglutinated materials are targets for what?

A

phagocytes

57
Q

What Ig is very effective for agglutination?

A

IgM–10 antigen sites per pentamer

58
Q

What does antibody neutralization do?

A
  • block interactions with host cell receptors and eventual entry
  • prevent toxins from entering cells
59
Q

Neutralized material will eventually…?

A

be ingested by phagocytes

60
Q

Are monomers better for neutralization?

A

Yes

61
Q

Antibodies bound to surfaces can be recognized by what component of the complement system?

A

C1q

62
Q

Antibody-C1q interaction induce a conformation change in the C1 complex…what does this activate?

A

C1s and C1r proteases

63
Q

What does C1s generate?

A

C4b and C2a creating classical C3 convertase

64
Q

The C3 converses lead to what deposition?

A

C3b

65
Q

Deposition of C3b will drive formation of what?

A
  • membrane attack complex—>cell lysis

- macrophage and neutrophil phagocytosis

66
Q

T-f—antibodies alone on the surface can be recognized by Fc receptors expressed on phagocytes?

A

True—multiple contacts will lead to phagocytosis

67
Q

Can monomeric or soluble antibodies activate cells via Fc receptors?

A

No

68
Q

T-f—infected cells often express microbial antigens on their surface?

A

True

69
Q

T-F—NK cells have Fc receptors that can recognize bound antibodies?

A

True—activation leads to cytotoxic function of NKs

[imporatant for virus or intracellular bacteria]

70
Q

What antibody is critical for early antibody responses and defense against extracellular microbes?

A

IgM

71
Q

Does IgM have a high or low affinity for antigen?

A

relatively low

72
Q

Surface bound IgM activates what>

A

complement pathway cascade

73
Q

Do IgG have a high or low affinity?

A

High—-have a long half-life

74
Q

What are the main differences between IgG subtypes?

A
  • hinge region
  • ability to fix complement
  • affinity for Fc receptors
75
Q

IgG3, IgG2, IgG4 and IgG1 is ordered in what order for ability to fix complement?

A

IgG3>IgG1>IgG2>IgG4

76
Q

IgG antibodies can engage 5 of 5 major B cell effector pathways?

A

false—4 of 5

  • complement pathway
  • Fc mediated phagocytosis
  • neutralization
  • Ab dependent cytotoxicity
77
Q

Does IgA have high or low affinity?

A

generally high

78
Q

How does IgA chiefly function (main effector model)?

A

neutralization

79
Q

IgE has high or low affinity?

A

High

80
Q

T-F—IgE bind constitutively to IgE receptor expressed on mast cells

A

True—multiple IgE antigen contacts leads to activation

Immuno Unit 3 Self (3 decks)

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