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Immunology - Exam #1 > Antibody Structure and Function > Flashcards

Antibody Structure and Function Flashcards

1
Q

Immunoglobulins can be _______ or ______ receptors

A

Membrane Bound or Soluble

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2
Q

What causes a resting B cell to generate antibody?

A

Encounter with antigen turns it into a plasma cell

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3
Q

What is an epitope?

A

An antigenic determinant

The part of an antigen to which an antibody binds

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4
Q

T or F. Most antigens have a single epitope.

A

False. Most antigens ahve multiple epitopes

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5
Q

What are epitopes usually made of?

A

Carbohydrates of pepride

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6
Q

Difference between DTwP and DTaP

A 
DTwP = Whole Cell Pertussis Vaccine
DTaP = Acellular Pertussis Vaccine
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7
Q

An immune response to _____ is triggered in an HPV vaccination.

A

Caspid

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8
Q

Where are epitopes recognized by antibodies typically located?

A

At the antigen surface.

There they can be directly bound

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9
Q

Two different types of epitopes an Ab can bind to.

A

Linear and Discontinuous

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10
Q

Difference between linear and confirmational/discontinuous epitopes.
How is this different from T Cells

A
  • Linear epitope binding happens to series of peptide in a row.
  • Discontinuous epitope binds to peptides adjacent to one another because they are disrupted and unfolded.
  • Ts Only Do Linear
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11
Q

What lymphocytes recognize confirmational epitope?

A

B Cells.

NO T Cells

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12
Q

What lymphocytes recognize linear epitopes?

A

B Cells and T Cells

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13
Q

What are Haptens?

A

Small molecules that are not immunogenic alone.

They can bind Igs and TCRs.

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14
Q

What do Haptens do?

A

They can induce immune responses when linked to a lager carrier.

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15
Q

Example of a Hapten?

A

Penicillin

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16
Q

Effect of Penicilin on bacteria

A

Binds bacterial transpeptidase and inactivates it

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17
Q

Effect of Penicillin on RBC

A

Modifies RBC Proteins to generate a foreign epitope

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18
Q

What happens to RBCs after they receive their hapten epitope?

A

B Cells are activated by antigen+TH2
Ab binding to RBCs
RBC destruction

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19
Q

What holds together the light and heavy chains?

A

disulfide bonds

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20
Q

Where can disulfide bonds be found?

A

Between light and heavy

In the Hinge Region

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21
Q

Names of the two light chains

A

Lambda and Kappa

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22
Q

Name the five heavy chains

A

Mu, Gamma, Alpha, Epsilon, Delta

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23
Q

The specificity of binding comes from the…

A

Antigen binding sites/Variable Region

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24
Q

What do you find when Ab is cleaved by Papain?

How many total fragments are generated?

A

Antigen-binding Fragment
Crystallizable Fragment
Three

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25
Q

What do you find when Ab is cleaved by pepsin?

How many total fragments are generated?

A

F(ab’)2 fragment
Chopped up base
2 Fragments

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26
Q

What function might F(ab’)2 have?

A

Naturally, none.

In labs, it can be used in binding studies.

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27
Q

Use of the hinge region?

A

Gives flexibility at antigen binding sites

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28
Q

Downside of the hinge region?

A

Susceptible to proteolysis by bacterial and host proteases

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29
Q

How many domains in heavy chain? Light Chain?

What are they?

A
  1. 3C, 1 V

2. 1C, 1V

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30
Q

Significance of V and C Regions?

A

V=Epitope Binding

C = Biological Fxn of Molecule

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31
Q

Describe the molecular structure of the Ab domains.

A

Two beta sheets held together by a disulfide bond

“Sandwich with a Toothpick”

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32
Q

Another name for hypervariable region?

A

Complementarity-Determining Region

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33
Q

What do hypervariable regions do?

A

They provide the actual antigen binding specificity.

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34
Q

How many HV regions are in an antigen binding site?

A

6 (3 on light and 3 on heavy)

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35
Q

Are the HV regions adjacent genetically?

A

No, hydrophobic regions come together from different parts of the genome in the process of protein folding.

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36
Q

Name the 5 types of Immunoglobulins

A

Ig G, M, D, A, E

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37
Q

Which immunoglobulins have no Hinge region?

What else is special about them?

A

IgM and IgE

Also have a 4th constant domain

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38
Q

Problems with the unique structure of IgM and IgE?

A

Less Flexibility of antigen binding.

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39
Q

What are isotypic differences between immunoglobulins?

A

Like IgG vs IgA

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40
Q

What are allotypic differences between immunoglobulins?

A

Variations of immunoglobulins seen because they come from the two different genes. Usually only very small differences.

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41
Q

What are idiotypic differences between immunoglobulins?

A

Like IgGs with different epitope binding sites

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42
Q

Why care about allotypical differences (3)

A 
May alter half life
May Affect subclass distribution
Associated with susceptibility to infectious and autoim. disease
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43
Q

How are allotypes inherited?

A

Autosomal dominant

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44
Q

T or F. Binding strength can be very variable between different antibody-epitope pairs.

A

True

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45
Q

What forces drive the antibody-antigen interaction?

A

Non-Covalent:

  • Electrostatic
  • Hydrogen Bonds
  • Van der Waals
  • Hydrophobic
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46
Q

What is affinity?

A

Strength of the interaction between the epitope and one antigen binding site.

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47
Q

What is avidity?

A

Strength of the sum of interactions between antibody and antigen. Also any other rxns that might be invovled (i.e. TCR, etc.)

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48
Q

Why might avidity differ from affinity.

A

Binding with both antigen binding sites can significantly increase the strength.

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49
Q

Explain how cross reactivity works.

A

Antiserum raised against antigen A also reacts against antigen B because they share an epitope.

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50
Q

Two scenarios in which cross-reactivity is very important.

A

Impt. for vaccines and laboratory reactions

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51
Q

How many Hs and Ns in Influenza?

A

16H and 9N

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52
Q

What are monoclonal antibodies.

A

Immortilizations of single clone of antibody-secreting cells

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53
Q

How are monoclonal antibodies made in the lab? (broad concept)

A

B Cells + Neoplastic (myeloma) cells

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54
Q

Steps of monoclonal antibody generation.

A
  1. Fuse B and Myeloma Cells
  2. Grow in drug-containing medium to select for hybrids
  3. Select for antigen-specific hybridoma
  4. Clone the winner
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55
Q

How are polyclonal antibodies made?

A

From serum of immunized animals. (goats, rabbits)

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56
Q

Concerns regarding polyclonal antibodies

A

Multiple specificities and affinities

Variation from batch to batch

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57
Q

Name the four types of therapeutic monoclonal antibody.

A

Mouse
Chimeric
Humanized
Human

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58
Q

Nomenclature for Chimeric

A

-ximab

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59
Q

Nomenclature for humanized

A

-zumab

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60
Q

Nomenclature for human

A

-umab

61
Q

Problems with therapeutic mouse antibody

When is it still useable

A

Patients develop anti-mouse antibodies

Diagnostic

62
Q

What mouse regions are maintained in humanized antibodies?

A

HVR

63
Q

Can therapeutic human antibody elicit an immune response?

A

yes

64
Q

Three types of immunoassays and level of detection.

A

Precipitation – 30ug/mL
Agglutination – 1 ug/mL
Radioimmunoassay/ELISA – 1 pg/mL

65
Q

Whats precipitation all about?

A

Antigens form large enough complexes to see with the naked eye.
Insensitive and rarely used.

66
Q

What is agglutination all about?

A

Usually hemaglutination

67
Q

What is ELISA all about?

A

Very sensitive. Good for studies of viruses and such

68
Q

To form the largest precipitates, what proportion of antibody to antigen is required?

A

Equivalence

69
Q

Aggregates are known to get stuck in _____ and _____

A

Kidneys and Joints

70
Q

Larger antigens are more prone to have _______ epitopes

A

More

Makes large antigens better for aggregation

71
Q

Do you have to be sensitized to have anti-A or B

A

No – prbs cross reactions with gut microbes

72
Q

Ab type used in hemagglutination

A

IgM

73
Q

Why is a different AB blood type baby fine?

A

Mom’s IgMs can’t cross the placenta

74
Q

Difference between Direct and Indirect Coombs Test?

A

Direct: anti-human Ig Abs (Coomb’s reagent) + fetal RBCs
Indirect: Mom’s Serum+Rh+ RBCs

After either, add anti-human antibody and assess aglut.

75
Q

What type of Ig is used in Coombs?

A

IgG

76
Q

Why don’t the IgGs agglutinate spontaneously?

A

They’re too small, so RBC without Ab can’t

77
Q

What is Coombs test even assessing?

A

Rhesus factor antibody response in mother and child (i.e. Rh- mom and Rh+ kid)

78
Q

Should a Rh- mother be worried about her first Rh+ child?

A

Probs not.

Should not have Abs developed till the 2nd time

79
Q

Steps in an ELISA

A
  1. Coat Wells with Antigen
  2. Add serum sample
  3. Add enzyme-labeled anti-human IgG
  4. Add substrate
80
Q

Steps in a Western Blot

A
  1. Dissociate proteins in SDS
  2. Run SDS-Page to separate by molecular weight
  3. Transfer to nitrocellulose
  4. Overlay with anti-serum
  5. Detect antibody with enzyme linked anti-IgG
81
Q

Tell me about immunoflouresence studies.

A

Put an antibody on with a fluorophore attached, send exciting light, pick up emitted light on microscope.
Use to identify structures (esp. in dev. bio)

82
Q

Explain Flow Cytometry.

A
  1. Incubate samples with Ab
  2. Each monoclonal Ab had differently colored labels
  3. Run through a small stream with a laser that can count based on the diff colors.
83
Q

Value of flow cytometry?

A

Qualitative, Rapid

Common in Diagnostic Labs.

84
Q

Fragments of genome seen in lambda chain? kappa chain? heavy chain?

A

l – VJC
k – VJC
h – VDJC

85
Q

Describe the steps of kappa chain generation

A
  1. Germline DNA undergoes VJ combination
  2. B cell DNA undergoes transcription into RNA transcript
  3. VJC is made via RNA splicing
  4. Translation into kappa chain polypeptide
86
Q

List the order of fragments coming together in heavy chain

A

DJ –> VDJ –> VDJC

87
Q

Significance of alrge number of gene segements in Ig loci?

A

Allow for A TON of recombinatory mechanisms

88
Q

What is the purpose of recombination signal sequences?

A

They prevent bonding of regions out of order

89
Q

Significance genetically of the 12 and 23 nuc. segments

A 
12 = 1 twist of DNA helix
23 = 2 twists of DNA helix
90
Q

What are the nucleotide segments involved in recombination signal sequences?

A

7-23-9 binds with 9-12-7

91
Q

Enzyme complex that conducts recombination.

Mentioned components.

A

VDJ Recombinase

RAGs, TdT, Artemis Nuclease

92
Q

What are RAGs

A

Recombination Activity Genes

Loop out intervening DNA to delete it

93
Q

Steps from cleaving out the loop to recombined DNA (6)

A
  1. RAG leaves DNA hairpins
  2. RAG nicks hairpins, generates palindromic P-nucleotides
  3. TdT adds in nucleotides at joining region
  4. Strand pairing
  5. Unpaired nucleotides are removes by exonuclease
  6. Gaps caused by DNA synth and ligation
94
Q

Three ways recombination can inadvertently promote diversity.

A
  1. TdT adds in nucleotides
  2. Imprecise Joining
  3. Unpaired nucleotide removal can lead to frameshift
95
Q

Initially, what heavy chain is made

A

IgM

96
Q

Why aren’t all Abs IgMs?

A

Isotype switching can happen later

97
Q

Naive mature B cells express what isotypes?

A

IgM and IgD

98
Q

What is addedd to the Ig following the C chain being splied in -

A

AAA

99
Q

Why are there two kinds of naive generated?

A

RNA contains both IgM and IgD components

They can be splicaed differently

100
Q

T or F. Alternative splicing = isotype switching.

A

False.

101
Q

Since B cell receptors lack the AA for intracellular signalling, they associate with…

A

Ig alpha and beta heterodimer

102
Q

Vaugely descripe B cell signalling

A

B cell binds, conformational change, activation of heterodimer, tyrosine kinase intracellular signalling

103
Q

What happens to B cells after activation?

A 
Ab Secretion
Somatic Mutation (more diversity)
Isotype switching
104
Q

How does the change from Membrane to secreted Ig happen?

A

Alternative RNA processing

105
Q

T or F. Somatic hypermutation will always lead to stronger antigen binding.

A

F. Can increase or decrease specificity or have a neutral effect.

106
Q

What mediates somatic hypermutation activity of CDR 1/2?

What does it do?

A

Activation-induced Cytidine deaminase

Cytosine->Uracil. Changes base pairs

107
Q

Outcome of isotype switching?

A

Igs with different C regions, but identical antigen specificity.

108
Q

Steps of Isotype Switching.

A
  1. IgM and IgD are produced.
  2. AID selectively targets S(mu) and S(gamma1) switch
  3. DNA of both switch regions is nicked
  4. DNA btw nicks is looped out
  5. IgG1 is produced
109
Q

What is AID?

A

Activation-Induced Cytosine Deaminase

Important in Somatic hypermutation AND isotype switching

110
Q

After isotype switching, can you go back?

A

No. DNA is spliced out.

111
Q

Effector fxns of Abs?

A

Neutralization (bind to prevent receptor binding)
Opsonization
Complement Activation

112
Q

Whats so cool about IgM?

A

Pentamer Structure

Can be transported in mucosal secretions

113
Q

IgM have _____ Affinity and _____ Avidity

A

Low Affinity and High Avidity

114
Q

Who is the first Ig synthesized in immune response.

A

IgM

115
Q

Roles of IgM

A

Activates complement

Agglutination

116
Q

___ stabilizes the IgM pentamer

A

J chain

117
Q

Which Ab has the highest conc. in the serum?

A

IgG

118
Q

How many IgG subclasses?

A

4

119
Q

Complement activation of the 4 subtypes?

A

IgG3 > IgG1 > IgG2.

Ig4 doesn’t do shit.

120
Q

Roles of IgG

A

Binds Fc receptors of neutrophils, macrophages, NKs

Complement Activation

121
Q

Difference between the 4 IgGs?

Which is especially prevalent?

A

Hinge Region Structure

IgG3 has a freakin huge hinge – very susceptible to proteases and shorter half life

122
Q

Whats unique about IgG4

A

Functionally Monovalent

123
Q

What does functionally monovalent mean?

A

Can dissociate at hinge region and recombine

Forms bivalent Ab molecules w/ 2 binding sites

124
Q

End effects of functional monovalence?

A

Less effective

125
Q

Secretory AgA is a….

A

Dimer with secretory component

126
Q

Subclasses of IgA?

A

IgA1 and 2

127
Q

Is IgA1 usually a monomer or dimer?

A

Monomer

128
Q

Is IgA2 usually a monomer or dimer?

A

Dimer

129
Q

Where do you tend to see IgA?

A

Mucosal Secretions

130
Q

Primary role of IgA? Response to this?

A

IgA does neutralization

Many bacteria produce IgA proteases to fuck it up

131
Q

IgA sucks at…

A

activating complement

Helps not kill epithelial barriers of mucosa in infection

132
Q

Which Abs have no hinge?

A

ME

133
Q

IgE is normally at a ___ concentration

A

Low

134
Q

What patient would you expect heightened IgE in?

A

Helminth infections or Allergies

135
Q

What does IgE bind?>

A

Fc receptor of Mast/Baso

136
Q

Where is IgD found?

A

URT

137
Q

Lowest half life?

A

IgE

138
Q

Relative frequency?

A

IgG
Middle IgA, M
Lowest ED

139
Q

Which Igs primarily do neutralization?

A

G,A

140
Q

Which Igs primarily do opsinization?

A

G1,G3

141
Q

Which Igs primarily do NK killing?

A

G1, G3

142
Q

Which Igs primarily do Mast cells?

A

E

143
Q

Which Igs primarily do complement system?

A

M, G1, G3

144
Q

Which Igs primarily do transport across epithelium?

A

A

145
Q

Which Igs primarily do transport across placenta?

A

G134

146
Q

Which Igs primarily do extravascular diffusion

A

G,A

147
Q

List the seven events of a B cell’s life

A
  1. V region assembly
  2. Generation of Junctional Diversity
  3. Assembly og Transcriptional Controlling elements
  4. Trans. activated with IgM and D
  5. Synthesis changes to secreted
  6. somatic hypermutation
  7. Isotype Switch
148
Q

Which two (of the seven event in a B cells life) are reversible?

A

Transcription of IgM and D

Synthesis changes from membrane to secreted antibdy.

Immunology - Exam #1 (5 decks)

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