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Core Concepts in Immunology > Lecture 19-23: Proteins of the Immune System > Flashcards

Lecture 19-23: Proteins of the Immune System Flashcards

1
Q

What are the five types of human antibody ?

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

How many types is there of IgA ?

A

2

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3
Q

How many types is there of IgD?

A

1

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4
Q

How many types is there of IgE ?

A

1

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5
Q

How many types is there of IgG ?

A

4

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6
Q

How many types is there of IgM ?

A

1

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7
Q

Where is IgA found ?

A

Mucosal areas such as the gut, respiratory tract, and urogenital tract. Also saliva, tears and breast milk

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8
Q

What do IgA antibodies form ?

A

Complexes that bind to multiple antigen molecules

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9
Q

What does IgD function as ?

A

An antigen receptor on B that have not been exposed to antigens

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10
Q

What does IgD activate ?

A

Basophils and mast cells

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11
Q

What does IgD’s activation of basophils and mast cells produce ?

A

Antimicrobial factors

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12
Q

What is the function of IgE ?

A

Binds to allergens and triggers histamine release from mast cells and basophils, protects against parasitic worms

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13
Q

What is the function of IgG ?

A

Provides the majority of antibody-based immunity against invading pathogens

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14
Q

What is the special function of IgG ?

A

The only antibody capable of crossing the placenta to give passive immunity to fetus

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15
Q

Where is IgM expressed ?

A

On the surface of B cells in a monomer form and in a secreted form (pentamer) with high avidity

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16
Q

What is the function of IgM ?

A

Eliminates pathogens in the early stages of B-cell mediated immunity before there is sufficient IgG

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17
Q

What are the outcomes of antibody production ?

A
  1. Antibody secretion
  2. Isotype switching
  3. Affinity maturation
  4. Memory B cell
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18
Q

What is the steps in antibody production by B-cells and plasma cells (T-cell dependent) ?

A
  1. Immunoglobulin receptors on B-cell surface recognise and attach to antigen which is then internalised and processed
  2. A fragment of the antigen combines with HLA class II -displayed on the B-cell surface
  3. Receptor on the T helper cell recognises complex of HLA class II and antigen fragment and is activated producing cytokines, which activate B-cell
  4. B cell is activated by cytokines and begins clonal expansion- some of the progeny become antibody producing plasma cells
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19
Q

What is the structure of an immunoglobulin ?

A
  1. Two fab regions
  2. Hinge region
  3. Fc region
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20
Q

What type of molecules are antibodies ?

A

Dynamic and flexible

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21
Q

How was the importance and fragility of the flexible hinge discovered ?

A

Cryo-electron tomography and particle electron tomography

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22
Q

How many immuglobulin regions does a light chain consist of ?

A

2

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23
Q

How many immunoglobulin domains does a heavy chain consist of ?

A

4

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24
Q

What type of cleavage site does an immunoglobulin have ?

A

Papain

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25
Q

What is the structure of immunoglobulin domains ?

A
  1. Two beta antiparallel sheets that surrounds a hydrophobic core
  2. One disulphide bond bridges the sheets
  3. Three loops present at one end of the structure form a potential binding surface
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26
Q

What provides the vast repertoire of immunoglobulin domains ?

A

Variations of the amino acid sequences of these loops

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27
Q

What binds to the complementarity determining regions or loops ?

A

Antibodies

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28
Q

How is a binding surface formed ?

A

Six complementarity determining regions come together

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29
Q

What are the characteristics of the immunoglobulin fold of the light chain constant region ?

A

3 plus 4 strands

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30
Q

What are the characteristics of the immunoglobulin fold of the variable region ?

A

4 plus 5 strands

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31
Q

What has a diversity region ?

A

Heavy chain

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32
Q

What are the two types of light chains ?

A
  1. Kappa
  2. Lambda
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33
Q

What are the first antibodies expressed ?

A

IgM and IgD

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34
Q

Where are nucleases only expressed ?

A

B-cells

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35
Q

Where are membrane bound and secreted forms of IgM expressed from ?

A

The same heavy chain locus

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36
Q

Where is the lambda light chain locus ?

A

Chromosome 22

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37
Q

Where is the kappa light chain locus ?

A

Chromosome 2

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38
Q

Where is the heavy chain locus ?

A

Chromosome 14

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39
Q

What is the organisation of heavy an light gene loci mediated by ?

A

VDJ recombinase enzyme, RAG1 and Rag 1 and other enzymes

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40
Q

What are variable gene regions constructed from ?

A

Gene regions

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41
Q

What is rearrangement/recombination of variable gene segments guided by ?

A

Flanking DNA/Signal sequences

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42
Q

How long are Ig domains in antibodies ?

A

70-110 amino acids

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43
Q

What are the steps in genetic recombination (VDJ) ?

A
  1. D to J recombination
  2. V to DJ recombination
  3. Transcription and splicing
  4. Translation and assembly
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44
Q

Where does genetic recombination in immunoglobulins occur ?

A

Developing lymphocytes including B and T cells

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45
Q

What does genetic recombination involve ?

A

Somatic hypermutation/recombination

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46
Q

What is each immunoglobulin composed of ?

A

Heavy and light chain

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47
Q

What does every heavy and light chain contain ?

A

Multiple copies of each gene segment (constant, variable, diversity and joining)

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48
Q

What does the light segment not contain ?

A

Diversity segment

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49
Q

What are the key enzymes in genetic recombination in immunoglobulins ?

A

Recombination activating genes 1 and 2 (Rag 1 and 2), terminal deoxynucleotidyl transferasae and a nuclease (artemis nuclease)

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50
Q

How does class switching occur ?

A

Changing constant regions

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51
Q

What do antibodies induce following oponisation ?

A

Effector responses

52
Q

What is communication with immune system mediated by ?

A

Fc region

53
Q

What is the function of Fab region ?

A

Antigen binding

54
Q

What is the function of Fc region ?

A
  1. Phagocytosis
  2. ADCC activation
  3. CDC activation
  4. Humoral tolerance
  5. IgG transport
55
Q

What does binding of IgG to an antigen do ?

A
  1. Immune complex formation
  2. Opsonisation by antibodies
56
Q

How do antibodies bind ?

A

Induced fit

57
Q

What is antibody analysis ?

A

Analysing antibody sequence, structure and posttranslational modifications

58
Q

What are the techniques used for antibody structure characterisation ?

A
  1. Gel electrophoresis
  2. Isoelectric focusing
  3. Ion exchange chromatography
  4. Size exclusion chromatography
  5. 2D electrophoresis
59
Q

What is the principle of X-ray crystallography ?

A

Scattering of xrays by electrons

60
Q

What is a crystal ?

A

An arrangement of protein units which are periodic in three dimensions

61
Q

What are some examples of protein misfolding ?

A
  1. Alzheimers
  2. Ameloidosis
62
Q

What is the molecular make up of ameloidosis ?

A

Clonal plasma cells secrete light chains which then form fibrils

63
Q

What is the most effective treament of ameloidosis ?

A

Melephalan and stem cell transplantation

64
Q

What are some antibody functions ?

A
  1. Activation of complement
  2. Antibody mediated cell cytotoxicity
  3. Phagocytosis
  4. Opsonisation
  5. Virus neutralisation
  6. Receptor internalisation
  7. Crosstalk with receptor signaling
65
Q

What is the function of neonatal receptors ?

A

Recycle antibodies

66
Q

What is the neonatal receptor ?

A

FcRn

67
Q

What is the Fcy receptor ?

A
  1. FcyRIa
  2. FcyRIIa
  3. FcyRIIIB
  4. FcyRIIb
  5. FvyRIIIa
68
Q

What are the complement receptors ?

A
  1. C1q
  2. MBL
69
Q

What receptor bins IgA and controls its activity ?

A

Fcalpha

70
Q

What receptor binds IgE ?

A

Fcepsilon

71
Q

What molecules are involved in binding IgA ?

A

Neutrophils, monocytes, macrophages, eosinophils

72
Q

What are the processes involved in IgA binding with its receptor ?

A
  1. Endocytosis
  2. Phagocytosis
  3. Microbe killing
73
Q

What are the molecules involved in IgE binding ?

A

B-cells, basophils, mast cells, eosinophils

74
Q

What are the processes controlled by receptor binding IgE ?

A
  1. Phagocytosis
  2. Microbe killing
  3. Hypersensitivity
75
Q

What does Fcy receptor bind ?

A

IgG

76
Q

What are the five types of Fcy receptor ?

A

Inhibitory:
FcyRIIb

Activatory:
FcyRI
FcyRIIa
FcyRIIIa
FcyRIIIb

77
Q

What cells does IgG receptor binding promote ?

A
  1. Neutrophils
  2. Monocytes
  3. Macrophages
  4. Eosinophils
  5. Dendritic cells
  6. NK cells
  7. Microglia
  8. Astrocytes
  9. Neurons
78
Q

What are the processes involved in IgG receptor binding ?

A
  1. Endocytosis
  2. Phagocytosis
  3. Microbe killing
  4. ADCC
79
Q

What controls the activity of IgG antibodies ?

A

Fc gamma receptors

80
Q

Where are type I transmembrane proteins found on ?

A

A wide range of immune cells and non-immune cells

81
Q

What influences the antibody affinity and binding kinetics ?

A

Complex glycoproteins

82
Q

What mediates the effector activities of IgG ?

A

Fc gamma receptors

83
Q

What happens following cell activation/inhibition ?

A

Activation of signalling cascades leading to effector or inhibitory responses involving immuno-tyrosine activation or inhibitory motifs

84
Q

Where is the neonatal receptor found ?

A

Endothelial cell, epithelial cells and antigen presenting cells

85
Q

Where is the neonatal receptor found ?

A

Placenta for transport of IgG form mothers milk to the foetus

86
Q

What is the neonatal receptor found in ?

A

Involved in recycling IgG and increasing serum concentration, increases half life, maintains high levels of IgG to fight infection

87
Q

What is the complement system ?

A

System of plasma proteins that recognise and interact with pathogens to mark them for destruction by phagocytosis

88
Q

What does amplification of cascade lead to ?

A

Activation of membrane attack complex

89
Q

What are the main steps in complement ?

A
  1. Oposonisation
  2. Chemotaxis
  3. Cell lysis
  4. Agglutination
90
Q

What are the three pathways of complement ?

A
  1. Classical
  2. MBL lectin
  3. Alternative
91
Q

How is complement activated ?

A

IgG binds to complement receptor C1q

92
Q

What influences antibody mediated activation of the complement cascade ?

A

Glycans

93
Q

Why can IgG-G0 react with MBL ?

A

No galactose

94
Q

What do all cells need ?

A
  1. Nucleic acids
  2. Glycans
  3. Proteins
  4. Lipids
95
Q

What do glycans play a primary role in ?

A

Immune recognition and immune evasion

96
Q

What are some roles glycans play in biological systems ?

A
  1. Differentiation
  2. Bacterial infection
  3. Ligand-receptor binding
  4. Viral attachment
  5. Viral entry/infection
  6. Cell growth and cytokinesis
  7. Cell-cell adhesion
  8. Metastasis
    9
97
Q

What is glycomics ?

A

The systemic study of all glycan structures of a given cell type or organism

98
Q

What is protein glycosylation ?

A

The post translational modification/attachment of sugars to proteins

99
Q

What is the most abundant postranslational modification ?

A

Protein glycosylation

100
Q

What are N-glycans attached to ?

A

Asparagines

101
Q

What are O-glycans attached to ?

A

Serines and threonines

102
Q

Where does glycosylation occur ?

A

ER and golgi

103
Q

How does glycosylation work ?

A

Large linked lipid precursor molecule is added to polypeptide chain on asparagine residue in the sequence on Asn-X-Ser where X is any amino acid except proline

104
Q

Where are N-glycans processed ?

A

In golgi and glcoproteins secreted in vesicles

105
Q

How is quality controlled in endoplasmic reticulum ?

A

Calnexin and calreticulin

106
Q

How is glucose removed from nascent polypeptide ?

A

Glucosiadases in ER

107
Q

What do incorrectledly folded proteins interact with ?

A

UDP-glucose

108
Q

How does immune evasion occur?

A

Sugars

109
Q

How do viruses enter cells ?

A

Carbohydrate binding proteins

110
Q

How do viruses bind to host cell lectins ?

A

Sugrads

111
Q

What is used to treat Influenza A and B ?

A

Tamiflu

112
Q

What is tamiflu ?

A

Neuraminidase

113
Q

How does neuramindase work ?

A

Enzyme which removes sialic acids from host cell glycoproteins which new virions need to exit the cell

114
Q

Where are glycans located ?

A

Fc and Fab regions

115
Q

What are glycans critical for?

A

Function of the antibody

116
Q

What does IgG0 interact with ?

A

MBL to activate complement

117
Q

What does desialylation of IVIg do ?

A

Abrogates anti-inflammatory properites

118
Q

What does loss of core alpha (1,6) fucose on IgG result in ?

A

Enhanced ADCC activity

119
Q

What are c-type lectin receptors used for ?

A

Detection and activation through carbohydrate recognition

120
Q

Where are c-type lectin receptors present ?

A

Dendritic cells

121
Q

What are lectins ?

A

Sugar binding proteins

122
Q

What are lectin depedent on ?

A

Ca +2

123
Q

What do lectins contain ?

A

Carbohydrate recognition domain

124
Q

What is the stucture of defensins ?

A

Have disulphide bonds which create secondary structures

125
Q

What can anti-TNF therapies be used for ?

A

Autoimmune disease for example rheumatoid arthiritis

126
Q

What is rituximab therapy for ?

A

Non-Hodgkins lymphoma

127
Q

What is herceptin therapy used for ?

A

Her2 positive metastatic breast cancer

Core Concepts in Immunology (22 decks)

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