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ODDR- Immunology > Introduction to the Immune System 3. > Flashcards

Introduction to the Immune System 3. Flashcards

1
Q

What are antibodies composed of?

A

They are Y shaped molecules copses of 2 light chains and 2 heavy chains

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2
Q

How heavy are the heavy chains that make up antibodies?

A

50 kDa

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3
Q

How heavy are the light chains that make up antibodies?

A

25 kDa

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4
Q

What hold the 4 polypeptide chains together in antibodies?

A

Disulphide bonds

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5
Q

What specifically do the disulphide bonds link in antibodies?

A

2 disulphide bonds link the heavy chains
1 disulphide bond links each light chain to its heavy chain partner
So 4 disulphide bonds in total

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6
Q

What are the 2 main groups of functions antibodies have?

A
  1. To recognise and bind antigens

2. To elicit effector functions

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7
Q

Name the 2 different regions of the antibody

A
  1. The variable region

2. The constant region

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8
Q

What function does the variable region complete?

A

It provides the antigen binding function of the antibody

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9
Q

What function does the constant region complete?

A

It elicits the effector function (eg recruits additional immune cells OR cells to destroy pathogens following antigen binding)

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10
Q

Where are the variable region found?

A

At the amino (end) terminals of the polypeptides

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11
Q

Where are the constant region found?

A

At the C terminus

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12
Q

Define affinity

A

The strength of binding of one molecule to another at a single site

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13
Q

Give an example of an event that shows affinity

A

The binding of a monovalent Fab fragment of antibody to a monovalent antigen

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14
Q

Define avidity

A

The sum of the strength of bonding of 2 molecules or cells to one another at multiple sites

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15
Q

Antibodies are bifunctional. What does this mean?

A

It means they have 2 functions:

  1. To recognise and bind antigens
  2. To elicit effector functions
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16
Q

How are antibodies digested?

A

By different proteases

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17
Q

What are proteases

A

An enzyme that cut up proteins

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18
Q

What has the digestion of antibodies allowed us to do?

A

Dissect antibodies an be able to view them at a molecular level to see what bit does what function

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19
Q

Name the 2 enzymes that perform important digestive functions

A
  1. Papain

2. Pepsin

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20
Q

What does papain do?

A

It cleaves the antibody to produce 2 Fab fragments and 1 Fc fragment

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21
Q

What does a Fab fragment do?

A

It recognises the antigen

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22
Q

Why is the Fc fragment given this name?

A

It is the easiest fragment to crystallises

fragment crytaliseable

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23
Q

Why is the Fab fragment given this name?

A

Means fragment antibody binding

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24
Q

What does an Fc fragment do?

A

It binds to cell receptors to recruit other ells of the immune system

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25
Q

What does pepsin do?

A

It cuts the antibody to give a F(ab’)2 fragment

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26
Q

Describe the F(ab’)2 fragment

A

It has 2 antigen binding sites as the 2 Fab arms are still linked together

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27
Q

Do the Fab and F(ab’)2 have the same AFFINITY for antibodies?

A

Yes it is the same

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28
Q

Do the Fab and F(ab’)2 have the same AVIDITY for antibodies?

A

No it is different

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29
Q

What are the 2 types of light chains found in humans?

A
  1. Kappa (k)

2. Lambda (λ)

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30
Q

Which type of light chains do each antibodies have?

A

Any particular antibody has either 2 K chains or 2 λ chains

never one of each

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31
Q

What is the average ratio of B cells prosecuting kappa light chained antibodies to lambda?

A

2:1

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32
Q

Name a situation where the ratio of B cells prosecuting kappa light chained antibodies to lambda?may be skewed?

A

If someone were to have cancer

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33
Q

What are the 5 different classes of antibodies called?

A
  1. IgG
  2. IgA
  3. IgM
  4. IgD
  5. IgE
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34
Q

Which heavy chains make up IgG?

A

Gamma chain

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35
Q

Which heavy chains make up IgA?

A

Alpha chain

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36
Q

Which heavy chains make up IgM?

A

Mui chain

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37
Q

Which heavy chains make up IgD?

A

Delta chain

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38
Q

Which heavy chains make up IgE?

A

Exelon

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39
Q

What 2 forms can IgA take?

A

The monomeric

The polymeric form (a diamer)

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40
Q

What 2 forms can IgM take?

A

The monomeric

The polymeric form (a pentamer)

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41
Q

What do both heavy and light chains contain?

A

A repeated similar domain called the immunoglobulin fold

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42
Q

How may immunoglobulin folds are there in IgG light chains?

A

2

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43
Q

How may immunoglobulin folds are there in IgG heavy chains?

A

4

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44
Q

Where is all variability in the antibody found?

A

At the amino (N) terminal domains of the light and heavy chains

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45
Q

Give some other examples of cells that have immunoglobulin folds but are not immunoglobulins?

A
  1. T cell receptors
  2. MHC
  3. CD5
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46
Q

Where is the antigen binding site found?

A

At the amino (N) terminal domains of the light and heavy chains (the variable regions)

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47
Q

What is each immunoglobulin fold composed of?

A

2 antiparallel beta pleated sheet held together by disulphide bonds?

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48
Q

What are beta strands linked by?

A

Flexible loops

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49
Q

What do the flexible loops linking beta strands allow?

A

Allow strands to alternate direction

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50
Q

What is amino acid sequence variability concentrated in?

A

In the hypervariable regions or Complementarity Determining Regions (CDRs)

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51
Q

What is located at the tip of each Fab arm?

A

3 CDRs in the heavy chain and 3 CDRS in the light chain

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52
Q

What dies CDR stand for?

A

Complementarity Determining Regions

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53
Q

What do the 6 CRDs at the tip of each Fab arm combine to generate?

A

Combine to generate antigen binding sites

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54
Q

How do changes in amino acid sequences lead to changes in antigen binding specificity?

A

Changes in amino acid sequence at hypervariable regions alter the Complementarity Determining Regions which in turn leads to changes in antigen binding specificity

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55
Q

What is Combinatorial diversity ?

A

Different specificities created by different combinations of heavy and light chains.

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56
Q

Antigen and antibody bind via non-covalent interactions which can be disrupted by what?

A
  1. High salt concentrations
  2. Extreme pH
  3. Detergents
  4. High concentrations of purified epitope
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57
Q

Name some of the non-covalent interactions which can bind Antigen and antibody?

A 
1. Electrostatic
forces
2. Hydrogen bonds
3. Hydrophobic forces
4. Van der Waals forces
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58
Q

Where are Electrostatic

forces found?

A

Between oppositely charged amino acid side chains on antibody and antigen

59
Q

What can disturb electrostatic forces?

A

High salt

60
Q

Where are Hydrogen bonds found?

A

When Hydrogen is shared between negatively charged atoms.

61
Q

What can disturb hydrogen bonds?

A

High salt

62
Q

Where are hydrophobic

forces found?

A

Found when Hydrophobic groups pack together, excluding water

Has a short range

63
Q

Where are Van Der Waals

forces found?

A

Where fluctuations in electron clouds occur leading to opposite polarisations in neighbouring atoms.

64
Q

What are antibodies used in?

A

Diagnostics
Research
In drugs

65
Q

What are the functions of different Ig classes determined by?

A

The Fc regions

66
Q

Gives some ways antibodies complete their function

A
  1. Neutralisation
  2. Opsonisation
  3. Activation of the complement pathway to act as opsonin or lysis.
67
Q

What is neutralisation

A

Antibodies bind to pathogen and toxins, and prevent binding to the cellular receptors pathogens used to gain entry to cells.

68
Q

What is Opsonisation?

A

The coating of pathogen with antibody

This results in phagocytes recognising the Fc region of that pathogen causing the phagocyte to engulf the pathogen

69
Q

Where are antibodies present

A 
In a lot of different places in our body:
Much 
Lining airway 
Serum
Fluid that bathes our tissues
70
Q

Describe the process of neutralisation

A
  1. Antibody blocks the binding of microbes to cells
  2. Antibody clocks the infection of adjacent cells
  3. Antibody clocks the blinding of toxin to cellular receptor
71
Q

What is the newest potential role of antibodies?

A

If an antibody bound to a virus is taken up by a cells an intracellular receptor called TRIM21 detects the antibody inside the cell and recruits the proteasome machinery

72
Q

What do proteasome do inside the cell?

A

The proteasome degrades the antibody virus complex.

73
Q

Where is TRIM21 found and what is it?

A

It is an enzyme found inside cells

74
Q

Name where our central (primary) lymphoid organs are found?

A
  1. Thymus (T cells)

2. Bone marrow (B cells)

75
Q

Name where our Peripheral (secondary) lymphoidal organs are found?

A
  1. The adenoids
  2. Tonsils
  3. Lymph nodes
  4. Spleen
  5. Peyer’s patches
  6. Appendix
76
Q

Define Antibody repertoire

A

The total range of antibody specificity

77
Q

What is the estimated Antibody repertoire ?

A

1 x 10^11

78
Q

Why is a diverse Antibody repertoire required?

A

required to recognise vast array of more rapidly evolving pathogens.

79
Q

what do dendritic cells do

A

Cells that have taken up antigens from the site of infection to the lymph nodes in order to display the antigens to keep the immune repose going

80
Q

What is the estimated total number of lymphocytes in the body?

A

4x10^11 and 2x10^12,

81
Q

Where does variation in Ig derive from?

A

Ig variation is derived from changes in the amino acid sequences which occur within the CDRs, altering the antigen binding sites.

82
Q

What is the problems with great Ig diversity?

A

Theres not enough genomic space

83
Q

What is the solution our body has to the lack of genomic space to code all the different Ig variations

A

Somatic Recombination.

84
Q

What have Ig genes in B cells been rearrange by?

A

Somatic Recombination.

85
Q

What are gene segments?

A

Variable regions of Ig genes are encoded in multiple pieces

86
Q

What is germline diversity?

A

Multiple choices for each gene segment

87
Q

What provides combinational diversity?

A

The process where by Segments are randomly selected and brought together in different combinations

88
Q

The variable region in light chains are encoded by what segments?

A

2 types of segment:

Variable (V) and Joining (J)

89
Q

The variable region in heavy chains are encoded by what segments?

A

3 types of segment:

Variable (V), Diversity(D) and Joining (J)

90
Q

Name the 3 sets of immunoglobulin chains

A
  1. Kappa light chain
  2. Lambda light chain
  3. Heavy light chain
91
Q

What MUST genes encoding the variable region be present in?

A

Must be present as multiple gene segment

92
Q

Name the 3 immunoglobulin loci

A
  1. Kappa chain locus
  2. Lambda chain locus
  3. Heavy chain locus
93
Q

Where is the Kappa chain locus present?

A

Chromsome 2

94
Q

Where is the lambda chain locus present?

A

Chromsome 22

95
Q

Where is the heavy chain locus present?

A

chromosome 14

96
Q

At the 5 prime end of each locus what is present?

A

A cluster of V (variable) gene segments

97
Q

What is each V segment associated with?

A

A leader (L) sequence

98
Q

What does the L sequence encode?

A

It encodes a signal or leader peptide that facilitates the transport of Ig protein through the endoplasmic reticulum

99
Q

Is the leader sequence present in mature Ig?

A

No it is cleaved before hand

100
Q

At the 3 prime end of each locus what is present?

A

A cluster of J (Joining) gene segments

101
Q

What do J gene segments code for?

A

The portions of variable region of Ig chains

102
Q

How are the 2 segments in light chains ( the variable and the joining) brought together?

A

They are Brought together by one somatic recombination event

103
Q

Describe the process of Light chain gene rearrangement.

A

1 .Gene rearrangement of V and J occurs via one somatic recombination event to give an exon

  1. The Gene is transcribed
  2. The remaining introns are removed during RNA splicing
  3. The leader sequence is translated targeting protein for secretion or expression on the cell surface.
  4. Leader sequence is cleaved off post translation
104
Q

What is V (D) J recombination?

A

A process by which B cells randomly assemble immunoglobulin gene segments (ie v, d, j gene segments) to form the function variable region exon

105
Q

When does V (D) J recombination occur?

A

During early development of lymphocytes

106
Q

What does somatic DNA recombination do during Light chain gene rearrangement?

A

The gene segments are rearranged to form a complete variable region coding sequence

107
Q

Give one word or phrase to describe each step in the process of Light chain gene rearrangement.

A
  1. somatic DNA recombination
  2. Transcription
  3. Splicing
  4. Translation
  5. Cleaving
108
Q

Describe the process of Heavy chain gene rearrangement.

A
  1. Gene rearrangement of D J via a somatic recombination event
  2. ANOTHER gene rearrangement occurs of V-DJ via a somatic recombination event to give a complete exon
  3. The Gene is transcribed
  4. The remaining introns are removed during RNA splicing
  5. The leader sequence is translated targeting protein for secretion or expression on the cell surface.
    6 . Leader sequence is cleaved off post translation
109
Q

What is a key difference between light and heavy chain rearrangement?

A

In light chain rearrangement there is only 1 gene rearrangement event (V-J joining)
In HEAVY chain rearrangement there are TWO gene rearrangement events (V-J joining AND V-DJ joining)

110
Q

What controls the V(D)J recombination?

A

Controlled by non-encoding, conserved DNA sequences

Recombination Signal Sequences (RSS)

111
Q

What does a Complete functional rearrangement require?

A

One of each type of segment is joined in the correct order and in the correct transcriptional orientation

112
Q

Where can recombination only occur?

A

Recombination can only occur between one gene segment flanked by a 12 spaced RSS and another with a 23 spaced RSS.

113
Q

How Many types of RSS are there?

A

2:
One with 23 base pair spacer
One with a 12 base pair spacer

114
Q

Approx how many V segments do we have in our heavy chains?

A

45

115
Q

Approx how many V segments do we have in our kappa light chains?

A

35

116
Q

Approx how many V segments do we have in our Lambda light chains?

A

30

117
Q

Approx how many D segments do we have in our heavy chains?

A

23

118
Q

Approx how many J segments do we have in our heavy chains?

A

6

119
Q

Approx how many J segments do we have in our kappa light chains?

A

5

120
Q

Approx how many J segments do we have in our lambda light chains?

A

4

121
Q

Why do the number of segments in each Ig vary in the population?

A

Because humans are very polymorphic

122
Q

Approx how many heavy chain combinations are there?

A

V x D x J
45 x 23 x 6
=6000

123
Q

Approx how many kappa light chain combinations are there?

A

V x J
35 x 5
= 175

124
Q

Approx how many lambda light chain combinations are there?

A

V x J
30 x 4
= 120

125
Q

Approx how many light chain combinations are there IN TOTAL?

A

potential kappa + potential lambda

175+120= 295

126
Q

Why are the number of potential light and heavy chains number very varied?

A

Because segment numbers are varied

Some combinations produce non-functional pseudogenes

127
Q

What is the third level of diversity called (after gremlin and combinatorial)?

A

Junctional diversity

128
Q

When does junctional diversity occur?

A

When selected gene segments have to be joined together

129
Q

Describe how junctional diversity is achieved

A
  1. RAG proteins cleave the DNA.
  2. Nucleotides are added or subtracted to make a viable joint by TdT (terminal deoxynucelotidyl transferase).
  3. The position of the cut adds P nucleotides to the sequence, whilst the TDT adds N nucleotides.
130
Q

What does RAG stand for in RAG proteins?

A

Recombinase-activating genes 1 and 2

131
Q

What are RAG protein responsible for?

A

For cutting and cleaning DNA

132
Q

Is the process of achieving junctional diversity efficient?

A

No there’s a lot of wastage because in the process of deleting and adding nucleotides we can get frame shifts

133
Q

Name the 3 layers of diversity in T cells and antibodies?

A
  1. Germline
  2. Combinatorial
  3. Junctional
134
Q

What can genetic immunological disorders affect?

A
  1. Severe combined Immunodeficencies (T and B cell function)
  2. Deficiencies in antibody production
  3. Phagocytic disorders
  4. Complement deficiencies.
135
Q

Which fragments of antibodies have the same AFFINITY?

A

the Fab and F(ab’)2

136
Q

What hold together the 2 antiparallel beta pleated sheets in each immunoglobulin fold?

A

Disulphide bonds

137
Q

Which fragments of antibodies have different AVIDITY?

A

the Fab and F(ab’)2

138
Q

Gamma heavy chains make up which class of antibodies?

A

IgG

139
Q

Alpha heavy chains make up which class of antibodies?

A

IgA

140
Q

Mui heavy chains make up which class of antibodies?

A

IgM

141
Q

What does the Fc region determine?

A

The different classes of antibodies

142
Q

Delta heavy chains make up which class of antibodies?

A

IgD

143
Q

Exelon heavy chains make up which class of antibodies?

A

IgE

144
Q

What is the immunoglobulin fold?

A

A repeated similar domain found on both light and heavy chains

ODDR- Immunology (6 decks)

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