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Immunity > Antibodies I > Flashcards

Antibodies I Flashcards

1
Q

Proteins present in mucosal secretions, blood, & tissue fluid

A

Antibodies

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2
Q

Bind to toxins, viruses, & bacteria, blocking their access to our cells

A

Antibodies

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3
Q

Antibodies are classified as

A

Immunoglobins (Ig)

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4
Q

The structure of all antibodies is based on a unit of

A

Four polypeptide chains

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5
Q

Antibodies are made up of

A

2 heavy chains and 2 light chains

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6
Q

Connect each heavy chain to its partner light chain, and connect the two heavy chains

A

Disulfide bonds

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7
Q

In a given Ig, the two heavy chains are always identical, as are the

A

Two light chains

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8
Q

Each Ig chain is divided into regions or domains consisting of around

A

110 amino acid residues

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9
Q

How many domains are in the

  1. ) Light chain?
  2. ) Heavy chain?
A
  1. ) 2

2. ) 4

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10
Q

The N-terminal domain on both the heavy and light chain are known as the

A

Variable domains (VL and VH)

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11
Q

The other domains are called

A

Constant domains (CL and CH1-3)

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12
Q

The heavy chain also contains a flexible

  • in the middle
  • allows the two arms of an Ig molecule to move with respect to eachother
A

Hinge domain

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13
Q

The antigen-binding sites are formed in the

A

Variable domains

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14
Q

Each Ig has two identical

A

Binding sites

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15
Q

Antigens are often macromolecules. An antibody binds to only a small portion of an antigen’s surface, called an

A

Epitope or antigenic determinant

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16
Q

Are both sterically and chemically complementary

A

Antibody and epitope

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17
Q

Sterically they fit together the way a lock fits its key. The interacting surfaces form multiple

A

Noncovalent bonds

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18
Q

A protein epitope typically contains 15-25 amino acid side chains, forming a ‘patch’ on the

A

Protein’s surface

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19
Q

The number of weak interactions is in the range of 50-200. A small number of side chains on both sides contribute the bulk of the

A

Binding energy

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20
Q

A small epitope, such as a short peptide or a small molecule, may interact with only a small portion of the

A

Combining site

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21
Q

Combining sites are formed from only a small part of each

A

Variable domain

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22
Q

Formed from complementarity-determining regions (CDR), loops of polypeptide chain at the ends of paired VH and VL domains

A

Combining site

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23
Q

Each V domain has 3

A

CDRs

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24
Q

The remainder of the V domains is largely B-sheet and comprises framework regions that hold

A

CDRs in place

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25
Q

When antibody V-domains are compared, CDR’s are much more different than framework regions. For this reason, CDR’s are also called

A

Hypervariable regions

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26
Q

CDR’s of both VH and VL make up the combining site; they are held in place by interactions between them and between their associated

A

CH1 and CL domains

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27
Q

A large, complex, antigen such as a protein has many

A

Epitopes

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28
Q

When the immune system reacts to such an antigen, although each individual Ig molecule is epitope-specific, the population of antibodies produced in the immune system can bind to many different

A

Epitopes

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29
Q

Since each distinct type of antibody is produced by a clone of plasma cells, the process of antibody production in response to a complex antigen is termed a

A

Polyclonal response

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30
Q

Not all epitopes are equally strong stimuli. Most of the antibodies formed may be antibodies to a few

A

Immunodominant epitopes

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31
Q

Dominant epitopes are typically present in

A

Many copies

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32
Q

The structure of the binding site depends on the nature of the

A

Epitope

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33
Q

If the epitope is a small molecule the binding site will be a

A

Pit in the surface of the antibody

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34
Q

This “pit” is necessary because only by surrounding the small molecule can enough weak bonds be made to allow for

A

Good binding

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35
Q

If the epitope is elongate, such as a peptide or carbohydrate chain, the binding site will be a

A

Groove

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36
Q

If the epitope is part of the surface of a protein, the binding site will be a

A

Lumpy Surface

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37
Q

Cleave antibodies at specific sites

A

Proteases

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38
Q

Produces two Fab fragments and one Fc fragment

A

Papain Cleavage

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39
Q

Univalent antigen-binding fragments composed of one entire Ig light chain and the amino terminal part of one of the Ig heavy chain, linked to each other by a disulfide bond

A

Fab

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40
Q

Contains the variable region of the immunoglobulin molecule, which contains the antigen-binding site, and the first constant region

A

Fab

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41
Q

Crystallizable fragments composed of the carboxyterminal parts of the heavy chain constant regions of both Ig heavy chains linked to each other by disulfide bonds

A

Fc

42
Q

Fc fragments are responsible for the effector functions of an

A

Immunoglobin

43
Q

(Fab’)2 contains two Fab fragments, that is, it contains

A

2 light chains and portions of 2 heavy chains

44
Q

(Fab’)2 contains two

A

Antigen combining sites

45
Q

May be used when it is desired to bind antibody to antigen without cross-linking

A

Fab fragments

46
Q

An Ig molecule consists of a heavy chain and a light chain. The light chain can be either a

A

Kappa or Gamma chain

47
Q

Genes for the Ig chains are present in segments. Each gene segment has multiple copies which are clustered in a distinct chromosomal region in the

A

Germline cells

48
Q

. For example, the Ig heavy chain gene complex consists of a constant (CH), a joint (JH), a diversity (D), and a variable (VH) region containing

A

11, 6, 25, and >130 gene segments, respectively

49
Q

Ig genes are made

A

Somatically

50
Q

During development of each antibodyproducing cell, its H- and Lchain genes are assembled from libraries of

A

Short gene segments

51
Q

In an antibody-producing cell, after assembly, the gene for Ig k light chain contains exons encoding the

A

Variable domain and the constant domain

52
Q

The V domain exon is composed of which two DNA segments?

A

V and J

53
Q

A functional V-region exon was assembled by selection of one V and one J segment from each array during

A

B cell development

54
Q

The unique structure of an antibody’s combining site, produced by choice of V, D, and J segments, and other mechanisms discussed below, defines its

A

Idiotype

55
Q

The receptors by which T cells recognize antigens (TCR = T cell Receptor) resemble antibody

A

Fab regions

56
Q

Each of the two chains of the TCR has a

A

Variable domain and a constant domain

57
Q

The variable domain of the TCR a-chain of the receptor is assembled from

A

V and J segments

58
Q

The variable region of the TCR B-chain is assembled from

A

V, J, and D segments

59
Q

The splicing machinery requires that a pair of sites to be cut and spliced include one with a 12-base spacer and one with a 23-base spacer. This ensures the correct splicing of

A

V, D, and J segments

60
Q

Because of the 12/23 requirement, a V segment cannot be spliced directly to a

A

J segment

61
Q

Recognize the conserved DNA signals and target the initial cuts

A

RAG1 and RAG2 gene products

62
Q

RAG stands for

A

Recombination of Antibody Genes

63
Q

The RAG1/RAG2 complex has the structure of a bacterial

A

Transposase

64
Q

RAG1 and RAG2 are found only in

A

Lymphocytes

65
Q

Other proteins essential for splicing are found in all cells and form part of the DNA repair machinery. Hence some DNA-repair deficiencies also lead to

A

Immunodeficiency

66
Q

Additional diversity is created at

A

Splice junctions

67
Q

V/D and D/J splice joints occur in

A

CDR3 regions

68
Q

Mechanisms that increase diversity at splice junctions increase combining-site diversity by a factor of about

A

10^5

69
Q

Randomly adds nucleotides to the cut ends of V, D, and J segments

A

DNA terminal deoxyribonucleotidyl transferase (TdT)

70
Q

Found only in developing lymphocytes and is sometimes used as a histochemical marker to identify them

A

TdT

71
Q

Repeated exposure to antigen results in progressive increase in

A

Antibody affinity (called affinity maturation)

72
Q

This is one reason why immunizations require a series of booster shots: each booster improves the

A

Affinity of the antibody

73
Q

The basis of affinity maturation is that, in germinal centers, there is high-level somatic mutation of the

A

Variable regions of immunoglobulin genes

74
Q

Mutation is random, so many mutations lower the affinity of the combining site for

A

Antigens

75
Q

Cells with such mutations are no longer stimulated by antigen, and

A

Die

76
Q

Cells with receptors which bind antigen the most tightly are most highly stimulated by it, proliferate most extensively, and occupy an increasing fraction of the

A

Population

77
Q

Antibody gene rearrangements sometimes results in

A

Cancer

78
Q

Rare errors in rearrangement can join the VDJ region of an immunoglobulin locus, not to a constant region segment, but to another gene entirely, sometimes on another chromosome. This may place this gene under the control of a powerful B-cell specific transcriptional enhancer close to the VDJ region. If the gene is involved in control of cell proliferation, overproduction may lead to uncontrolled cell division and formation of a clone of malignant cells. This is the origin of the chromosomal translocation seen in

A

Burkitt Lymphoma

79
Q

The class (or isotype) of the antibody is defined by the

A

Heavy chain

80
Q

Each class of antibody has a heavy chain with a different

A

Amino acid sequence

81
Q

The five immunoglobulin classes are designated

A

IgA, IgG, IgM, IgE, and IgD

82
Q

How many subclasses does

  1. ) IgG have?
  2. ) IgA have?
A
  1. ) 4

2. ) 2

83
Q

Subclasses have distinct functional roles; for example, IgG made in response to polysaccharide antigens is mostly

A

IgG2

84
Q

There are two different kinds of light chain, designated

A

Kappa (k) and gamma (y)

85
Q

An antibody-producing cell makes one and only one kind of

A

Light chain and heavy chain

86
Q

Recognize only a single epitope

A

Monoclonal antibodies

87
Q

Antibody-producing cells do not live long in culture. They are immortalized by fusing them with

A

Tumor Cells

88
Q

Individual fused cells are then cloned and each clone must be screened for production of antibody to the desired

A

Antigen or epitope

89
Q

Monoclonal antibodies are made in

A

Mice

90
Q

DNA encoding the CDR’s of their V domains can be cloned and sequenced and then incorporated into human

A

H- and L-chain genes

91
Q

Antibodies produced in this way are called

A

Humanized antibodies

92
Q

By genetic engineering proteins can be produced that contain part of an

A

Antibody chain

93
Q

For example, an experimental mode of anti-cancer therapy uses Fab fragments of an anti-tumor antibody to target a protein toxin to

A

Tumors

94
Q

Makes only one type of light chain and one type of heavy chain (‘allelic exclusion’)

A

Each B lymphocyte

95
Q

Successful assembly of one heavy-chain gene on one chromosome prevents rearrangement on the

A

Other

96
Q

The appearance of these chains on the plasma membrane may create an intracellular signal that prevents further

A

Re-arrangement

97
Q

Membrane and secreted forms of the same immunoglobulin are created by different patterns of

A

RNA splicing

98
Q

B cells, prior to antigenic stimulation, make immunoglobulin as a

A

Transmembrane protein

99
Q

In B cells, exons encoding the transmembrane and cytosolic domains of the Ig are retained when the primary transcript is spliced; in plasma cells they are

A

Excised

100
Q

Antibodies of primary and secondary immune responses are

A

Different

Immunity (33 decks)

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