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Year Three - Immunology > Immunology Physiolgy > Flashcards

Immunology Physiolgy Flashcards

1
Q

What is the function of the immune system?

A

It is the body’s ability to resist or eliminate pathogens, which are harmful foreign materials, from the body

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2
Q

What are the two components of the immune system?

A

Innate

Adaptive

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3
Q

What component of the immune system is activated first?

A

Innate

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4
Q

When is the innate immune system created?

A

Birth

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5
Q

When is the innate immune system activated?

A

If a pathogen breaches the physical barriers

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6
Q

Is the innate immune system specific or non-specific? What does this mean?

A

Non-specific

This means that it will produce the same response to every pathogen it meets as it has no memory

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7
Q

Is the adaptive immune system specific or non-specific? What does this mean?

A

Specific

This means that the cells involved in this response remember the cells that they fought and the antigens that they presented

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8
Q

What are the two divisions of the adaptive immune system?

A

Humoral

Cellular

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9
Q

What is the function of the humeral immune system? What immune cells are involved?

A

It secretes antibodies to fight against antigens

B-lymphocytes

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10
Q

Which pathogens does the hummoral immune system destroy?

A

Free-floating pathogens

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11
Q

What is the function of the cellular immune system? What immune cells are involved?

A

It secretes cytokines to attack pathogens

T-lymphocytes

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12
Q

Which pathogens does the hummoral immune system destroy?

A

Cells that have been infected by pathogens

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13
Q

What is the first line defence mechanism?

A

The physical and chemical barriers of the innate immune system

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14
Q

What are the three physical barriers of the innate immune system?

A

Skin

Mucous membranes

Mucociliary escalator

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15
Q

What are the three physical barriers of the innate immune system?

A

Skin

Mucous membranes

Mucociliary escalator

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16
Q

What is the mucociliary escalator?

A

It is the process in which mucus and cilia move mucus up and out of the respiratory tract

The epithelial cells are able to coat cell surfaces in mucous, which traps pathogens, preventing entry to the body

The cilia are hair-like structures found in epithelial cells, which are able to sweep the trapped pathogens in mucus away from the lungs

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17
Q

What are the four chemical barriers of the innate immune system?

A

Lysozymes

Acid

Mucus

Defensins

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18
Q

What are lysozymes? How do they destroy pathogens?

A

They are enzymes consistent of bactericidal properties

They are involved in digesting the bacterial walls of microbes and thus destroying them

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19
Q

In what four secretions are lysozymes present in?

A

Sebum

Tears

Perspiration

Urine

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20
Q

How does acid destroy pathogens?

A

It has a low pH, which bacteria are unable to grow in

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21
Q

In what three secretions are acid present in?

A

Sweat

Gastric secretions

Vaginal secretions

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22
Q

How does mucus destroy pathogens?

A

The viscous nature of mucous traps bacteria, which can then be actively cleared by the mucociliary escalator in the lungs or peristalsis of the gut

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23
Q

What are defensins?

A

They are proteins produced by the cells of the innate immune system

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24
Q

What are the two types of defensins?

A

Beta Defensins

Alpha Defensins

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25
Q

When is the second line defence mechanism activated?

A

When the physical and chemical external barriers fail to destroy the pathogen

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26
Q

What are the five components of the second line defence mechanism?

A

Infection recognition molecules

Inflammatory response

WBCs

Cytokines

Complement system

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27
Q

In the innate system, which receptors are involved in recognising pathogens?

A

Pattern recognition receptors (PRRs)

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28
Q

What are PRRs?

A

These are infection recognition receptors located on immune cells, such as macrophages and dendritic cells

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29
Q

What is the main subtype of PPRs?

A

Toll-like receptors (TLRs)

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30
Q

What do PRRs bind to?

A

Pathogen associated molecular patterns (PAMPs)

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31
Q

What are PAMPs?

A

An arrangement of carbohydrates, lipids and nucleic acids on the surface of a pathogen that signal to a phagocyte that a cell is foreign

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32
Q

What are the three functions of the inflammatory response?

A

Destroying foreign pathogens

Facilitating tissue response

Promoting healing

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33
Q

What activates the inflammatory response?

A

The recognition of PAMPs and DAMPs by the innate immune system, which leads to the release of pro-inflammatory cytokines (chemical mediators)

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34
Q

Describe the process of the inflammatory response

A

The release of cytokines increase vascular permeability and cause endothelial cells of neighbouring blood vessels to express cellular adhesion molecules (CAMs)

This enables leukocytes to migrate to the affected tissues

These cells then destroy the infectious agents and clean up dead tissue

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35
Q

What causes the cardinal signs of inflammation?

A

The release of chemical mediators - histamine and bradykinin

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36
Q

What are the four cardinal signs of inflammation?

A

Pain

Calor

Rubor

Tumor

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37
Q

What is another term for WBCs?

A

Leukocytes

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38
Q

What are the seven types of WBCs?

A

Neutrophils

Monocytes

Eosinophils

Basophils

NK Cells

Phagocytes

Mast cells

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39
Q

Are neutrophils granular or agranular leukocytes?

A

Granular

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40
Q

What two types of pathogens do neutrophils destroy?

A

Bacteria

Fungus

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41
Q

What is the most abundant leukocyte type?

A

Neutrophils

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42
Q

What is the lifespan of neutrophils?

A

2-3 days

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43
Q

How do neutrophils activated?

A

In response to damage or pathogens, tissues produce chemokines which recruit neutrophils in a process called chemotaxis, allowing neutrophils to locate the site of infection

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44
Q

How do neutrophils destroy pathogens? (2 mechanisms)

A

They phagocytose microorganisms and subsequently digest them by released granules into the phagosome

They release substances to attract monocytes

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45
Q

Are monocytes granular or agranular leukocytes?

A

Agranular leukocytes

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46
Q

What pathogens do monocytes destroy?

A

Bacteria

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47
Q

What is the unique feature of monocytes?

A

They are circulating leukocytes, which typically remain in the blood for around 8 hours before migrating into tissue where they differentiate into macrophages or dendritic cells

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48
Q

How do macrophages destroy pathogens? (2 mechanisms)

A

They phagocytose microorganism and digest them by releasing granules into the phagosome

They also secrete cytokines which modulate the immune response

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49
Q

What is the function of dendritic cells?

A

These cells form a link between the innate and adaptive immune system

They assist in T cell activation during the adaptive immune response

They are the only cell type that can activate naïve T cells

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50
Q

Are eosinophils granular or agranular leukocytes?

A

Granular leukocytes

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51
Q

What pathogens do eosinophils destroy?

A

Parasites

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52
Q

Where are eosinophils located?

A

These cells generally spend an hour in peripheral blood and are mainly present in tissues

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53
Q

How do eosinophils destroy pathogens?

A

They consist of granules, which contain major basic protein (MBP), cationic protein and peroxidase

These molecules are toxic to parasites

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54
Q

Are basophils granular or agranular leukocytes?

A

Granular leukocytes

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55
Q

What pathogens do basophils destroy?

A

Allergens

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56
Q

Where are basophils located?

A

Blood

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57
Q

What is the lifespan of basophils?

A

2 weeks

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58
Q

How do basophils destroy pathogens?

A

These cells contain histamine granules

They cause local inflammatory responses through their interaction with IgE

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59
Q

What type of hypersensitivity reactions are basophils involved in?

A

Type I hypersensitivity reactions

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60
Q

What two pathogens do NK cells destroy?

A

Viruses

Cancerous cells

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61
Q

What are the two types of receptors found on NK cells?

A

Activating receptors

Inhibitory receptors

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62
Q

What do activating receptors on NK cells bind to?

A

Molecules expressed on the cell surface of infected or damaged host cells

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63
Q

What do inhibiting receptors on NK cells bind to?

A

Host MHC I molecules

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64
Q

How are NK cells activated?

A

The NK cell evaluates the signals received through the activating and inhibitory receptors

The receptor type that sends the strongest signal determines whether it is activated or inhibited

In cases where a NK cell encounters a cell with absent or reduced MHC I expression, the signals provided by the damaged or infected cell to the activating receptor overpower those sent through the inhibitory receptor

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65
Q

How do NK cells destroy pathogens? (2 mechanisms)

A

They release cytolytic granules containing perforin and granzyme enzymes

They releases interferon-gamma and tumour necrosis factor alpha

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66
Q

What is the function of perforin enzymes?

A

They create a pore within the cell membrane of the target cell

This allows the granzyme enzymes to enter and destroy the cell

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67
Q

What is the function of granzyme enzymes?

A

Apoptosis

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68
Q

What are the two functions of interferon-gamma and tumour necrosis factor alpha?

A

They activate macrophages

They enhance the cytotoxic effects of NK cells

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69
Q

NK cells have a similar action to that of cytotoxic T lymphocytes. What are the three differences between NK cells and Tc lymphocytes?

A

NK cells produce a rapid response

NK cells lack immunological memory

NK cells don’t require priming by an antigen in order to initiate a response

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70
Q

What is the function of phagocytes?

A

They clear up cells and antigens through phagocytosis

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71
Q

What is phagocytosis?

A

This process involves engulfing a pathogenic invader or antigenic material

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72
Q

What five WBCs are considered to as phagocytes?

A

Macrophages

Neutrophils

Monocytes

Mast cells

Dendritic cells

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73
Q

What two molecules activate phagocytes?

A

Cytokines

Bacterial endotoxins

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74
Q

How do phagocytes move to the infected area?

A

Chemotaxis

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75
Q

Describe the process of phagocytosis

A

When a phagocyte comes into contact with a pathogen, receptors on the phagocyte surface bind and adhere to that pathogen

This allows the phagocyte to engulf the pathogen into a vesicle, known as phagosome

The phagosome then fuses with lysosome enzymes, which degrades and destroys the pathogen

The waste products are then presented on the phagocyte as antigens (antigen-presenting cell)

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76
Q

What is the function of antigen-presenting cells?

A

They can then activate other cells and alert them to the fact that there is a foreign pathogen present in the body

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77
Q

Are mast cells granular or agranular leukocytes?

A

Granular leukocytes

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78
Q

What is contained within the cytoplasm of mast cells?

A

Histamine

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79
Q

What is the function of mast cells?

A

They cause inflammation in the host

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80
Q

What is a hypersensitivity reaction?

A

This is an undesirable reaction produced by the normal immune system

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81
Q

How can mast cells produce a hypersensitivity reaction?

A

On initial exposure to an allergen, B-cells are stimulated by CD4+ cells to produce IgE antibodies

The IgE antibodies bind to Fc receptors on the surface of mast cells and basophils, which is a process referred to as sensitisation

In cases where the allergen enters the body again, they bind to the antibodies attached to the sensitised mast cells and basophils, which results in these cells being activated and releasing chemical mediators, such as histamine

These mediators result in multiple effects such a vasodilation and increased permeability of local capillaries

The increased permeability of the capillaries allows more immune responding cells to gain entry from the blood to the capillaries and for fluid to leak into tissues

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82
Q

What are cytokines?

A

They are proteins used in cell-signalling

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83
Q

What five cells produce cytokines?

A

Macrophages

Lymphocytes

Mast cells

Endothelial cells

Fibroblasts

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84
Q

What division of the immune system are cytokines involved in?

A

They are involved in both the innate and adaptive immune system

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85
Q

What are the four types of cytokines?

A

Chemokines

Interferons

Interleukins

Tumour Necrosis Factor (TNF)

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86
Q

What is the function of chemokines?

A

They induce chemotaxis in local cells

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87
Q

Which cells produce chemokines?

A

Macrophages

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88
Q

What cells respond to cytokines?

A

Those that have chemokine receptors on them

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89
Q

What occurs when chemokine receptors have been activated?

A

They activate phospholipase C, leading to the release of calcium from intracellular stores

This then results in varying actions depending on the chemokine subtype that activated the cell

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90
Q

What are the two types of chemokines?

A

Pro-Inflammatory Chemokines

Homeostatic Chemokines

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91
Q

What are the three stimuli for pro-inflamamtory chemokines?

A

Infection

Proinflammatory cytokines

Microbial products

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92
Q

What is the function of pro-inflammatory chemokines?

A

They allow immune cells, such as neutrophils and monocytes, to exit the bone marrow and locate affected tissues

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93
Q

When are homeostatic chemokines produced?

A

They are constitutively produced, which means that the body maintains basal levels without the need for a stimulus

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94
Q

What are the two function of homeostatic chemokines?

A

They allow T cells and dendritic cells to migrate and circulate through secondary lymphoid organs in search of potential pathogens (immune surveillance)

They are involved in the development of lymph organs and positioning of cells within lymphoid tissues

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95
Q

When are interferons released?

A

In response to pathogens and tumour cells

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96
Q

What are the three main classifications of interferons?

A

Type I

Type II

Type III

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97
Q

What is another term for type I interferons?

A

Interferon-alpha

Interferon-beta

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98
Q

Which cells produce type I interferons?

A

Almost all body cells

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99
Q

What are the two functions of type I interferons?

A

They interfere with viral replication

They help the immune system fight viral infections

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100
Q

What causes the release of type I interferons?

A

Microbial products

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101
Q

What does type I interferon bind to?

A

Interferon receptors on the same and neighbouring cells

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102
Q

What two types of signalling are type I interferons involved in?

A

Autocrine signalling

Paracrine signalling

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103
Q

What are the two functions of type I interferons?

A

To change gene expression within the cell. This leads to the destruction of viral mRNA and prevents host and viral protein translation

They also upregulate NK cell ligands and MHC I on the cell surface. Therefore, NK cells and cytotoxic T cells are more likely to detect and attack virus-infected cells

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104
Q

What is another term for type II interferons?

A

Interferon-gamma

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105
Q

What three cells produce type II interferons?

A

NK cells

Cytotoxic T cells

Th1 cells

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106
Q

What two molecules stimulate the release of type II interferons?

A

IL-12

IL-18

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107
Q

What are the two functions of type II interferons?

A

They activate macrophages and increases their ability to kill pathogens by enhancing pinocytosis and lysosome function

They also upregulate MHC II expression, which promotes antigen-presentation and effective phagocytosis

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108
Q

What is another term for type III interferons?

A

Interferon-delta

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109
Q

What three cells produce interleukins?

A

T-lymphocytes

Monocytes

Macrophages

110
Q

What are the three functions of interleukins?

A

Promotion of B & T Lymphocyte Production

Neutrophil & NK Cell Activation

Vascular Permeability

111
Q

What is the main cell type that produces TNF? What causes this production?

A

Macrophages

When they encounter an endotoxin

112
Q

What are the five functions of TNF?

A

Local Induction of Apoptosis

Vascular Permeability

Neutrophil Chemotaxis

Pro-Inflammatory State

Appetite Suppression

113
Q

What do cytokines released in response to inflammation cause?

A

The the endothelium to produce selectin on its surface

114
Q

What is another term for the complement system? Why?

A

Complement cascade

In all pathways, there is a cascade effect, in which the activation of one protein results in the sequential interactions with another protein, resulting in its activation

115
Q

What are the three pathways that activate the complement system?

A

The Classical Pathway

The Mannose-Binding Lectin Pathway

The Alternative Pathway

116
Q

What activates the classical pathway?

A

It is activated when a complement protein, known as C1q, binds to an antigen-antibody (immune) complex

117
Q

What occurs when the classical pathway is activates?

A

This triggers cleavage of the subsequent complement proteins in the cascade, resulting in production of C3 convertase and its downstream effects

118
Q

What divisions of the immune system is the classical pathway involved in?

A

Innate

Adaptive

119
Q

How is the classical pathway involved in the adaptive immune system?

A

Due to its involvement in antigen-antibody complexes

120
Q

What organ produces mannose-binding lectin?

A

Liver

121
Q

What is the function of mannose-binding lectin?

A

To detect carbohydrates containing mannose on the surface of pathogens

This then activates a protease called MASP

122
Q

What is the function of MASP?

A

It cleaves complement components, which activates a similar pathway to the classical pathway, eventually producing C3 convertase.

123
Q

How is the alternative pathway activated?

A

The direct binding of complement proteins to a microbe/antigen

124
Q

What occurs when the alternative pathway is activated?

A

This results in spontaneous hydrolysis of C3 into small amounts of factor C3b, which combined with other factors to produce C3 convertase

125
Q

What occurs when C3 convertase has been activated?

A

It divides the complement protein C3 into a large fragment (C3b) and a small fragment (C3a)

This will then activate C5, which in turn activates C6, C7, C8 and C9 in a cascade

126
Q

What is the function of C3a?

A

It is pro-inflammatory and can act as an anaphylatoxin

127
Q

What is the function of C3b?

A

It acts as an opsonin and a precursor for C5 convertase

128
Q

What are the four ultimate effects of the complement system?

A

Opsonisation

Lysis of Pathogens

Chemotaxis

Inflammation

129
Q

What is opsonisation?

A

It refers to the binding of an opsonin to an invading cell or organism, which enhances the efficiency of phagocytosis as it increases the likelihood of binding occurring between a phagocyte and a pathogen

This is achieved by increasing the number of binding sites available to the phagocyte and reducing the repellent negative charge that exists at the surface of all cells

130
Q

How doers the complement system cause opsonisation?

A

The binding of C3b to antigens on the pathogen stimulates neutrophils and macrophages to phagocytose pathogens

131
Q

What three molecules are classed as opsonins?

A

Complement proteins

Antibodies

Plasma proteins (mannose binding lectin)

132
Q

How does the complement system result in lysis of pathogens?

A

The fusion of C5b, C6, C7, C8 and C9 molecules facilitates the formation of the membrane attack complex (MAC)

133
Q

What is the function of MAC?

A

It ruptures the bacterial cell membrane, allowing extracellular fluid to enter the pathogen, which results in the osmotic rupture of the cell membrane and death

134
Q

What is chemotaxis?

A

It is the process in which a cell migrates in response to an extracellular chemical gradient

135
Q

How does the complement system result in chemotaxis?

A

The production of C5a attracts neutrophils and macrophages to the site of infection and causes extravasation of leucocytes from capillaries to tissues

136
Q

How does the complement system result in inflammation?

A

It is caused by the complements C3a, C4a and C5a

These proteins bind to mast cells and basophils to cause degeneration

The histamine and serotonin released increase vascular permeability

137
Q

What is the third line defence mechanism?

A

The adaptive immune system

138
Q

When is the third line defence activated?

A

When the innate immune system fails to destroy the pathogen

139
Q

What are the two immune cells involved in the adaptive immune system?

A

T-cells

B-cells

140
Q

What division of the adaptive immune system are T-cells involved in?

A

Cellular

141
Q

Where are T-cells produced?

A

Bone marrow

142
Q

Describe the production of T-cells

A

They originate from haematopoietic stem cells, which initially differentiate to form common myeloid and lymphoid progenitor cells

143
Q

Where do T-cells mature?

A

Thymus

144
Q

Describe the maturation of T-cells

A

The lymphoid progenitors will move from the bone marrow and travel to the thymus via the blood

145
Q

What are T-cells referred to as in the thymus?

A

Thymocytes

146
Q

What are two processes do T-cells undergo in the thymus?

A

Positive selection

Negative selection

147
Q

What is positive selection?

A

It involves selecting T-lymphocytes with T-cell receptors capable of interacting appropriately with host MHC molecules

In cases were thymocytes are able to interact with the MHC, they survive

However, if they are unable to interact, they are destroyed by apoptosis

148
Q

What is negative selection?

A

It involves identifying thymocytes that interact too strongly with self-antigens within the thymus – as these cells have a higher likelihood of being self-reactive and attacking our own cells

Thymocytes that react too strongly, are destroyed by apoptosis

149
Q

What do thymocytes divide into if they survive both positive and negative selection?

A

CD4+ cells

CD8+ cells

150
Q

What determines if thymocytes divide into CD4+ or CD8+ cells?

A

This depends on whether their TCR recognises an MHC class I-presented antigen or an MHC class II-presented antigen

151
Q

What causes CD4+ and CD8+ cells to differentiate into Th and Tc cells?

A

Once they have encountered antigens within secondary lymphoid organs

152
Q

What type of receptors do T-cells develop in the thymus?

A

T-cell receptors (TCR)

153
Q

Which process results in a diversity of TCRs?

A

V(D)J recombination

154
Q

What is V(D)J recombination?

A

This is a process of genetic changes that create a diverse selection of antigen binding sites within TCRs on naïve T lymphocytes

155
Q

Why is V(D)J recombination important?

A

This means that, when T lymphocytes are released from the thymus and encounter an antigen, there will be more chance that the antigen will be recognised by one of the TCR binding sites that have been developed

156
Q

What are the three classifications of T-cells?

A

Naïve T-Lymphocytes

T-Helper Lymphocytes

Cytotoxic T-Lymphocytes

157
Q

What are naive T-cells?

A

They are cells that have not encountered their specific antigen

158
Q

How are naive T-cells activated?

A

APCs use MHC molecules to present antigens, that can complement their binding sites

159
Q

What happens when T-cells are activated?

A

They they proliferate and differentiate into different T lymphocytes

160
Q

What are the two co-receptors that T-cells can use to bind to the MHC molecules?

A

CD4

CD8

161
Q

What do CD4+ T-cells differentiate into?

A

Helper T-cells

162
Q

What do CD8+ T-cells differentiate into?

A

Cytotoxic T-cells

163
Q

What are the three functions of Th cells?

A

Activation of other immune cells

Releasing cytokines

Assisting B-cells to produce antibodies

164
Q

What triggers activation of Th cells?

A

These cells are activated by binding to the antigens on an antigen-presenting cell

165
Q

What occurs when Th cells are activated?

A

Clonal selection

166
Q

What is clonal selection?

A

This is when a clone of activated helper T-cells and a clone of memory helper T-cells are formed

167
Q

How do Th cells recognise self and foreign antigens?

A

CD4+ receptors

168
Q

When do CD4+ receptors function?

A

When they bound to MHC II, which is a molecule found on all antigen presenting cells (APC’s)

169
Q

What is the function of Tc cells?

A

They kill their target cells by releasing cytotoxic granules into the target cell

170
Q

What pathogens do Tc cells mainly destroy?

A

Virally infected cells

171
Q

When are Tc cells activated?

A

These cells are activated by binding to the antigens on an antigen-presenting cell

172
Q

What occurs when Tc cells are activated?

A

Clonal selection

173
Q

What are the three mechanisms in which Tc cells destroy pathogens?

A

They release IFN and TNF-a, which have direct anti-viral and anti-tumour effects

They release cytotoxic granules, containing perforin and granzyme proteins. This eventually leads to apoptosis

They express FasL on the cell surface, which then binds to the Fas receptor on its target cell. . This binding results in down-stream effects within the target cell that triggers the caspase cascade and causes apoptosis

174
Q

How do Tc cells recognise self and foreign antigens?

A

CD8+ receptors

175
Q

When do CD8+ receptors function?

A

When they are bound to MHC I, which is a molecule found on all nucleated cells

176
Q

What molecule allows APCs to present antigens on their surface?

A

Major histocompatibility complex (MHC) molecules

177
Q

What is another term for MHC?

A

Human leukocyte antigen (HLA)

178
Q

What chromosome codes for MHC?

A

Chromosome 6

179
Q

What are the two types of MHC?

A

MHC class I

MHC class II

180
Q

Where are MHC I molecules found?

A

On the surface of all nucleated cells in the body

181
Q

How many proteins make up MHC I?

A

One

182
Q

What do MHC I molecules display?

A

Self-markers

Intracellular foreign antigens (viruses)

183
Q

How do infected host cells activate T-cells?

A

If a host cell becomes infected by an intracellular pathogen, the class I MHC molecules present antigens from this pathogen on its cell surface

184
Q

How do damaged/malignant host cells activate T-cells?

A

The self-markers displayed via the MHC I molecules become altered

The altered MHC I signal alerts the immune system that these host cells are damaged and should be destroyed by the immune system

185
Q

Where are MHC II molecules found?

A

They are found on professional antigen presenting cells

186
Q

How many proteins make up MHC II?

A

Two

187
Q

What are the three types of professional APCs?

A

Dendritic cells

Macrophages

B-lymphocytes

188
Q

What cells present both MHC I and MHC II molecules?

A

Professional APCs

189
Q

What do MHC II molecules display?

A

Extracellular antigens from pathogenic invaders (bacteria)

190
Q

What do Th1 cells produce? What is its function?

A

IFN-Y, TNF, IL-2

This results in clearance of intracellular pathogens, autoimmunity and chronic inflammation

191
Q

What do Th2 cells produce? What is its function?

A

IL-4, IL-5 and IL-13

This results in clearance of extracellular pathogens and allergens

192
Q

What do Th17 cells produce? What is its function?

A

IL-17, IL-22 and IL-21

This results in tissue inflammation, autoimmunity and clearance of certain extracellular pathogens

193
Q

What division of the adaptive immune system are B-cells involved in?

A

Humeral

194
Q

What are the two functions of B-cells?

A

They produce antibodies

They present antigens to T-cells

195
Q

What do B-cells mature into when they are activated?

A

Plasma cells

OR

Memory B-cells

196
Q

Where are B-cells produced?

A

Bone marrow

197
Q

Describe the production of B-cells

A

They originate from haematopoietic stem cells, which initially differentiate to form common myeloid and lymphoid progenitor cells

198
Q

Where do B-cells mature?

A

Bone marrow

199
Q

Describe the maturation of B-cells

A

The lymphoid progenitor cells remain in the bone marrow for maturation

200
Q

What three processes do B-cells undergo in the bone marrow?

A

Positive selection

Negative natural selection

B-cell receptor (BCR) formation

201
Q

What are the three ways in which B-cells can be activated?

A

Helper T-Cell Activation

Helper T-Cell Independent Activation

Memory B-Cell Activation

202
Q

How does Th cell activation lead to B-cell activation?

A

When an antigen is recognised by a a helper T-lymphocyte, it migrates towards the B-cell to activate it

203
Q

What is Th cell independent activation?

A

This occurs when B lymphocytes are activated directly by antigens found within secondary lymphoid organs in a process that does not require help by T lymphocytes

204
Q

What is memory B-cell activation?

A

This is when a memory B cell re-encounters an antigen that is able to bind to its specific BCR

205
Q

What to activated B-cells differentiate into?

A

Short-lived plasma cells

206
Q

What two types of antibodies do short-lived plasma cells produce?

A

IgM

IgG

207
Q

Where do short-lived plasma cells migrate to?

A

Secondary lymphoid organs, where they enter B-cell follicles or germinal centres of a lymph node

208
Q

What occurs in secondary lymphoid organs?

A

This is where lymphocytes are activated by foreign antigens

209
Q

List five secondary lymphoid organs

A

Lymph nodes

Spleen

Tonsils

Adenoids

Peyer’s patches

210
Q

What occurs in primary lymphoid organs?

A

This is where T-cells and B-cells mature

211
Q

List two primary lymphoid organs

A

Thymus

Bone marrow

212
Q

What three processes occur when B-cells enter the germinal centres?

A

The B-cells proliferate

The B-cells undergo somatic hypermutation which changes the affinity of their receptor. The receptors are then tested for their affinity

They B-cells undergo immunoglobulin class switching

213
Q

What is immunoglobulin class switching?

A

This is the process by which B cells become able to produce a different class of immunoglobulin in response to the same antigen

214
Q

Where do B-cells migrate to after germinal centres? What occurs?

A

Bone marrow

They differentiate into a long-lived plasma cell or memory B cell

215
Q

What is another term for antibodies?

A

Immunoglobulins

216
Q

What shape are antibodies?

A

Y-shaped

217
Q

What cells produce antibodies?

A

Differentiated B-cells, called plasma cells

218
Q

What are the two forms of antibodies?

A

A soluble form - found free-floating in the bloodstream

A fixed, membrane bound form - attached to the surface of a B-cell

219
Q

What are antibodies referred to as when they are found on the surface of B-cells?

A

B-cell receptors (BCRs)

220
Q

How many chains make up an antibody?

A

2 heavy chains

2 light chains

221
Q

How many antigen binding sites are found on antibodies?

A

Two

222
Q

What makes up a light chain?

A

A small polypeptide chain

223
Q

What is the function of the light chain?

A

It is the section that binds to the antigen to form the antibody-antigen complex

224
Q

What makes up a heavy chain?

A

A bigger polypeptide chain

225
Q

What is the function of the heavy chain?

A

It chain is the section not involved in the binding of the antigen

226
Q

What are the two regions found on antibodies?

A

Fc region (fragment crystallisable)

Fab regions (fragment antigen binding)

227
Q

What do Fab regions contain?

A

The variable domains of light and heavy chains

228
Q

What is the function of the Fab region?

A

It gives the antibody its antigen specificity

229
Q

What region differs between antibodies - Fab or Fc?

A

Fab

230
Q

What do Fc regions contain?

A

They contain the constant domains of the heavy chains

231
Q

What is the function of the Fc region?

A

This determines the antibody class

232
Q

What chain classifies antibodies?

A

The heavy chain

233
Q

What is the most prevalent antibody classification?

A

IgG antibodies

234
Q

What are the two functions of IgG antibodies?

A

It forms an important part of the secondary antibody response to an antigen

It is able to cross the placenta and consequently transfer passive immunity from mother to foetus

235
Q

What is the most prevalent antibody classification in secretions?

A

IgA antibodies

236
Q

What four secretions are IgA antibodies found in?

A

Saliva

Tears

Breast milk

Mucous

237
Q

What do IgA antibodies form?

A

A dimer

238
Q

What is a dimer?

A

This is when a a joining chain connects 2 Y-shaped molecules, giving it four antigen-binding sites in total

239
Q

What is the function of IgA antibodies?

A

They are neutralising antibodies

240
Q

What is the initial antibody classification produced during foetal development and in primary infections?

A

IgM

241
Q

Do IgM antibodies have a low or high avidity? What does this mean?

A

High avidity

This means that their antibody-antigen complex is strong

242
Q

Do IgM antibodies have a low or high affinity? What does this mean?

A

Low affinity

This means that the strength of a single epitope antibody interaction is weak

243
Q

What do IgM antibodies exist as?

A

Pentameters

244
Q

What are pentameters?

A

This is five antibodies connected by a joining chain, with ten antigen-binding sites in total

245
Q

Where are IgD antibodies present?

A

On the surface of B-cells

246
Q

What are the two functions of IgD antibodies?

A

They produce B-cells

They produce antibodies

247
Q

What two antibodies are expressed by all naive B-cells?

A

IgD

IgM

248
Q

What two cells are IgE antibodies present on?

A

Mast cells

Basophils

249
Q

What are the two functions of IgE antibodies?

A

When they bind to mast cells and basophils, they trigger their release of histamine

They are involved in the body’s response to parasitic infections

250
Q

What reactions are IgE antibodies associated with?

A

Allergic reactions, including including atopic disease (asthma, dermatitis) and anaphylaxis

251
Q

What are the five functions of antibodies?

A

Opsonisation

Neutralisation

Complement Activation

Immune Complexes

Antibody-Dependent Cell-Mediated Cytotoxicity

252
Q

How do antibodies act as opsonins?

A

They bind to to the pathogen, which allows better recognition by phagocytes

Phagocytes then bind to the antibodies via their Fc receptors and initiate phagocytosis

253
Q

How do antibodies cause neutralisation of pathogens?

A

They can prevent pathogens from accessing cells by blocking different parts of the bacterial or viral cell surface

254
Q

What complement system pathway do antibodies activate?

A

Classical

255
Q

How do antibodies activate the classical complement pathway?

A

They bind to microbial surfaces

256
Q

How do antibodies form immune complexes?

A

They bind to multiple antigens

257
Q

What occurs when immune complexes are formed?

A

They are cleared through the filtration of the blood, in organs like the liver and spleen

258
Q

What is antibody-mediated cellular cytotoxicity?

A

It is a process in which antibodies can initiate the killing of pathogens or target cells via immune cells from the innate immune system

259
Q

How do antibodies cause antibody-mediated cellular cytotoxicity?

A

The antibodies bind to the antigen on the target cell via the Fab region

The FC antibody receptor can then bind to a number of immune cells, such as NK cells, macrophages, neutrophils and eosinophils, in order to activate them

260
Q

What is immunological memory?

A

It refers to the ability of the immune system to recognise and respond to previously encountered antigens

261
Q

How is immunological memory formed?

A

During the primary immune response, memory cells are formed

This means that in the secondary immune response, when these memory cells meet their specific antigen again, they rapidly proliferate and differentiate into plasma cells

262
Q

What antibodies are produced in the highest concentration for primary infections?

A

IgM

263
Q

What antibodies are produced in the highest concentration for secondary infections?

A

IgG

264
Q

What is the advantage of immunological memory?

A

In the secondary immune response, there is a higher volume of antibodies produced faster

265
Q

What is tolerance?

A

When T-cell and B-cells are unresponsive to self tissue

266
Q

What are the two types of tolerance?

A

Central

Peripheral

267
Q

How do B-cells develop central tolerance?

A

Immature B cells that recognise self antigen in the bone marrow are negatively selected and die through apoptosis

268
Q

How do T-cells develop central tolerance?

A

T cells in the thymus that recognise self-peptide plus self-MHC with high affinity are negatively selected and die through apoptosis

269
Q

Why is peripheral tolerance important?

A

This is because some cells that can recognize self will still enter the periphery

270
Q

In what two ways do T-cells develop peripheral tolerance?

A

Anergy

T-regulatory cells

271
Q

What is anergy?

A

This is when T cell recognise an antigen presented on an MHC molecule however do not respond as there is no costimulation

Year Three - Immunology (4 decks)

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