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IMS - Immunology > Introduction to B cells and antibodies > Flashcards

Introduction to B cells and antibodies Flashcards

1
Q

What are the three types of signals that antigen-presenting cells deliver to naive T cells?

A
  • Activation
  • Survival
  • Differentiation
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2
Q

Label the T cell activation types from 1-3

A
  1. Activation
  2. Survival
  3. Differentiation
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3
Q

Label the cytotoxic T cell activation diagram from a to g

A

a - MHC-I

b - T-cell receptor

c - B7

d - CD28

e - IL-2

f - IL-2 receptor

g - Kill

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4
Q

What are naive T cells?

A

T cells that have not been exposed to an antigen

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5
Q

What does a naive T cell become once activated?

A

A primed T cell that proliferates and differentiates into either cytotoxic or helper T cells

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6
Q

What is the affinity of resting T cells to interleukin 2?

A

Moderate

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7
Q

What is the affinity of activated T cells to interleukin 2?

A

High

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8
Q

What does the binding of IL-2 to IL-2 receptors on T cells promote?

A

The T cell to enter the cell cycle, proliferate and differentiate

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9
Q

What are the specific antigens of the humoral immunity?

A
  • IgD
  • IgM
  • IgG
  • IgA
  • IgE
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10
Q

What is the role of an IgD receptor?

A

Antigen receptor for virgin B cells

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11
Q

What is the role of an IgM receptor?

A

Agglutination

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12
Q

What is the role of an IgG receptor?

A

Opsonisation

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13
Q

What is the role of an IgA receptor?

A

Protection of mucosa

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14
Q

What is the role of an IgE receptor?

A

Inflammation and protection against helminths

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15
Q

What are the non-specific complementary responses of humoral immunity?

A
  • Cytolysis
  • Chemotaxis
  • Inflammation
  • Opsonisation
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16
Q

What are the 4 stages of B cell activation by virus?

A
  1. B cell binds virus through viral coat protein.
  2. Virus particle is internalised and degraded.
  3. Viral proteins are presented to T cell which activates B cell.
  4. Activated B cells produce antibodies against viral coat protein.
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17
Q

What are the 4 stages of B cell activation by bacterium?

A
  1. B cell binds bacterial polysaccharide epitope linked to bacterial toxoid.
  2. Antigen internalised and processed.
  3. Antigen epitope presented to T cell.
  4. Activated B cell produces antibody against polysaccharide antigen on bacterium surface.
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18
Q

Where are B cells activated?

A

In lymphatic tissue where they remain

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19
Q

How do B cells respond to foreign antigens?

A
  • Engulf
  • Fragment
  • Present their epitopes on MHC-II molecules
  • Differentiate into plasma cells
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20
Q

What type of foreign antigens do B cells respond to?

A

Unprocessed antigens or antigen-presenting molecules

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21
Q

What recognises antigen-presenting B cells?

A

T helper cells

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22
Q

Label the B cell activation diagram from a to g

A

a - B cell receptor

b - B cell recognising unprocessed antigen

c - Costimulation by several interleukins

d - Proliferation and differentiation

e - Plasma

f - Memory cells

g - Antibodies

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23
Q

What do T helper cells do once they recognise B cells?

A

Secrete IL-2, IL-4, IL-6 which co-stimulate B cells to differentiate into plasma cells

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24
Q

What do plasma cells do?

A

Secrete antibodies that are specific to the initial stimulating antigen

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25
Q

Some B cells differentiate into plasma cells when activated, what do the others do?

A

Differentiate into memory B cells

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26
Q

How many polypeptide chains are there in an antibody?

A

4

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27
Q

What are the 4 chains of an antibody?

A

Two identical heavy chains and two identical light chains

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28
Q

Label the antibody diagrams from a to k

A

a - antigen-binding site

b - light chains

c - carbohydrate chain

d - antigen-binding site

e - heavy chains

f - stem region

g - hinge region

h - antigen-binding site

i - light chain

j - carbohydrate chain

k - heavy chain

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29
Q

How many amino acids make up the heavy chain of an antibody?

A

Approximately 450

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30
Q

How many amino acids make up the light chain of an antibody?

A

Approximately 220

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31
Q

What binds a light chain to a heavy chain in an antibody?

A

One disulfide bond

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32
Q

What binds two heavy chains in an antibody?

A

Two disulphide bonds at the mid-region forming a hinge region

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33
Q

What do both light and heavy chains posses in an antibody?

A

Variable regions and constant regions

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34
Q

What is the role of variable regions on antibody chains?

A

To confer specificity

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35
Q

Where are variable regions found on the antibody chains?

A

At the tips of the chains and at the apex of the antibody arms

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36
Q

How many antigen-binding sites does each antibody have?

A

2

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37
Q

What are hinge regions on antibodies for?

A

To allow the antibody the flexibility to bind to antigens in widely separated places

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38
Q

What is the constant region of an antibody?

A
  • Neary the same in different antibodies
  • Found on heavy and light chains
  • Not associated with antigen binding
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39
Q

Where does the constant region of an antibody vary slightly between different classes?

A

On the heavy chain

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40
Q

What are the five classes of antibodies?

A
  • IgG
  • IgA
  • IgM
  • IgD
  • IgE
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41
Q

Label the antibody isotypes diagram from a to i

A

a - IgG

b - IgE

c - IgD

d - IgM

e - disulphide bond

f - joining chain

g - IgA

h - joining chain

i - secretory protein

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42
Q

What does the binding of the antigen-binding site of an antibody with an antigen cause?

A
  • Neutralisation
  • Agglutination
  • Precipitation
43
Q

What is antibody neutralisation?

A

When an antibody covers the biologically active portion of a microbe or toxin

44
Q

What is antibody agglutination?

A

When an antibodies cross-links cells to form a clump

45
Q

What is antibody precipitation

A
46
Q

What does the exposed fragment crystalisable portion of an antigen promote following antigen binding?

A
  • Complement fixation
  • Opsonisation
  • Activation of NK cells
47
Q

What is complement fixation?

A

Where the Fc region of an antibody binds to a complement protein; thus, activating the complement

48
Q

What is opsonisation?

A

When the Fc region of an antibody binds to phagocyte receptors, promoting phagocytosis of the pathogen

49
Q

What is the activation of NK cells?

A

When the Fc region of the antibody binds to an NK cell triggering the release of cytotoxic chemicals

50
Q

What is a complement?

A

A system of numerous serum proteins acting in sequence that complement antibody activity in specific and non-specific immune responses

51
Q

What is the complement immune system involved in when activated inappropriately or exaggerated?

A

Immunopathology

52
Q

What are the complement proteins?

A
  • C1, C2, C3, C4, C5, C6, C7, C8, C9
  • Factor B, Factor D and Properdin
  • Mannose binding protein [MBP]
53
Q

What are the complement receptors?

A

CR1, CR2, CR3

54
Q

Label the complement sequence from a to g

A

a - antigen

b - antibody

c - Antigen-antibody complex activates C1

d - Factor B, factor D and factor P (properdin)

e - Polysaccharides on surface of microbe

f - Membrane attacking complex

g - Microbial membrane

55
Q

Which pathways is/are activated by microorganisms in the complement immune system?

A

Alternative pathway and Lectin pathway (both innate)

56
Q

Which pathway(s) is/are activated by antigen/antibody complexes in the complement immune system?

A

The classical pathway - specific

57
Q

What complement proteins are involved in the alternative pathway?

A
  • C3
  • Factor B
  • Factor D
  • Properdin
58
Q

What complement proteins are involved in the lectin pathway?

A
  • MBP
  • C2
  • C4
59
Q

What complement proteins are involved in the classical pathway?

A
  • C1
  • C2
  • C4
60
Q

Describe the 15 steps of the classical pathway

A
  1. IgM/IgG antibody binds to antigen epitopes.
  2. C1 binds to the Fc region of antibodies.
  3. C1r activates C1s which is a proteinase.
  4. C1s cleaves C4.
  5. C4b binds to antigen; C4a remains in fluid phase.
  6. C1s cleaves C2.
  7. C2b binds to antigen; C2a remains in fluid phase.
  8. C2b is a proteinase that cleaves C3.
  9. C3b binds to antigen; C3a remains in fluid phase.
  10. C2b cleaves C5.
  11. C5b doesn’t spontaneously bind; C5a in fluid phase.
  12. C5b binds C6, C7 and C8 in fluid phase.
  13. C5b678 binds to the lipid-bilayer.
  14. C9 inserts a hole into the membrane.
  15. Microorganism is lysed by the membrane attack complex.
61
Q

What is the reaction caused by the membrane attack complex described as?

A

An enzymatic cascade

62
Q

What does the membrane attack complex do?

A
  • Form pores in membranes of microorganisms.
  • Kills gram-negative bacteria, enveloped viruses and some protozoan parasites.
63
Q

How do gram-positive bacteria protect themselves against complement protein-mediated lysis?

A

Thick peptidoglycan cell walls

64
Q

How do fungi protect themselves against complement protein-mediated lysis?

A

Thick chitin cell walls

65
Q

Where does the classical pathway stop when attacking gram-positive bacteria

A

C5 cleavage

66
Q

What effect does complement protein-mediated lysis have on gram-positive bacteria?

A
  • Doesn’t directly kill them.
  • Plays an important part in their elimination from the body by other biological effects.
67
Q

What other biological effects from complement protein-mediated lysis aid the elimination of gram-positive bacteria from the body?

A

The biological activities of complement cleavage products C3a, C5a and C3b

68
Q

What type of complement cleavage products are C3a and C5a?

A
  • Anaphylatoxins that activate mast cells.
  • Chemotaxins that attract phagocytes (neutrophils and mononuclear phagocytes).
69
Q

What type of complement cleavage product is C3b?

A

An opsonin that enables phagocytes to recognise and bind to antigens and phagocytose them.

70
Q

What type of immunity is the alternative pathway found in?

A

The innate immunity

71
Q

What does the innate immunity not involve?

A

Antibodies

72
Q

In the alternative pathway, what do Factors B and D and Properdin interact with?

A

Microbial surface polysaccharides

73
Q

What biological activity is activated by the alternative pathway?

A
  • Membrane attack complex
  • C3a and C5a
  • Opsonisation by C3b
74
Q

What is a xenograft?

A

A tissue graft or organ transplant from a donor of a different species from the recipient.

75
Q

What occurs when the immune system recognises a xenograft?

A

Hyperacute rejection

76
Q

What mediates hyperacute rejection?

A

Naturally occurring antibodies to 𝝰-Gal.

77
Q

What are the naturally occurring antibodies to 𝝰-Gal?

A
  • Gala1
  • 3Galb1
  • 4GlcNAc
78
Q

Where is 𝝰-Gal found?

A

As a residue on cell surface glycoproteins and glycolipids on animal cells.

79
Q

What enzyme is used to synthesize 𝝰-Gal?

A

a1, 3Galactosyl transferase

80
Q

What animal species lack a1,3Galactosyl transferase?

A

Humans, apes and old world monkeys - lost during evolution.

81
Q

Why do humans recognise 𝝰-Gal as foreign?

A

Humans do not express 𝝰-Gal epitopes.

82
Q

Humans have [high/low] titres of antibodies to the 𝝰-Gal epitope.

A

high

83
Q

What is believed to induce cross high titres of 𝝰-Gal antibodies in humans?

A

Cross-reactive microbial antigens in the gut

84
Q

Which 4 steps occur when an organ graft that is hyperacutely rejected?

A
  1. Antibodies enter donor blood vessels and bind to 𝝰-Gal epitopes on endothelial cells.
  2. Complement is activated and neutrophils are attracted to the site destroying the endothelial cells.
  3. Thrombus formation blocks the vessels.
  4. The organ dies of oxygen deprivation within hours.
85
Q

Define xenogeneic

A

An adjective that describes a tissue as belonging to a different species.

86
Q

What are the two pathways for acute immune rejection of xenogeneic tissues?

A
  • Direct - incompatible MHC-II on animal cells.
  • Indirect - incompatible MHC-I on animal cells.
87
Q

Define immunogenic

A

Able to activate an immune response

88
Q

What are immunogenic components of the extracellular matric of different animal species?

A
  • Collagen and elastin
  • Glycosaminoglycans
89
Q

Define immunological memory

A

The ability of the immune system to quickly and specifically recognize an antigen that the body has previously encountered and initiate a corresponding immune response.

90
Q

What remains after an immune response?

A

Memory T and B cells.

91
Q

What can memory T and B cells do if they re-encounter the same antigen again?

A

Quickly proliferate.

92
Q

What is used to measure immunological memory?

A

The antibody tire

93
Q

How does the antibody titre change when exposed to a new antigen?

A

Increases after contact and then steadily decreases after the immune response.

94
Q

What is the initial contact with an antigen called?

A

The primary response

95
Q

What is the secondary response?

A

When an antigen is encountered a second time and the memory cells become activated.

96
Q

What happens in the secondary response?

A

Memory cells quickly proliferate and produce vast quantities of mostly IgG antibodies.

97
Q

What forms the basis of vaccination?

A

Immunological memory

98
Q

What is the correlation between old age and immune function?

A

Negative: as old age increases, immune function decreases.

99
Q

What happens to the function of T cells in old age?

A

They become less responsive to antigens

100
Q

Why do T cells become less responsive in old age?

A

Atrophy of the thymus and a decrease in thymic hormones

101
Q

What is associated with the decrease in T cells in old age?

A

Decrease in B cells

102
Q

How often are influenza vaccinations provided for the elderly?

A

Every year

103
Q

Why are influenza vaccines given to the elderly so often?

A

Because they take longer to increase their antibody titre because of their decreased levels of B and T cells.

IMS - Immunology (6 decks)

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