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Disease Mechanisms > Immunology - Innate and Adaptive Immune System > Flashcards

Immunology - Innate and Adaptive Immune System Flashcards

1
Q

From where are the cells of the immune system derived?

A

They are all initially derived from stem cells in the bone marrow, which differentiate into the various cell lineages.

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2
Q

How are immune cells primarily distinguished?

A

By the molecules that they express on the cell surface (markers). They are named using the CD system.

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3
Q

Which cell types are derived from myeloid stem cells?

A

Mast cells

Leukocytes

Phagocytes

Dendritic cells

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4
Q

Which cells types are derived from lymphoid stem cells?

A

Dendritic cells

Lymphocytes

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5
Q

Name the three types of leukocytes.

A

Basophils

Eosinophils

Neutrophils

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6
Q

Which cells are derived from monocytes?

A

Macrophages and phagocytes.

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7
Q

What are the different types of T cells?

A

Cytotoxic T Cells (TC)

Helper T Cells (TH)

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8
Q

What do B cells differentiate into?

A

Plasma Cells.

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9
Q

Which cell types are involved in the initial recognition of infection agents?

A

Lymphocytes.

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10
Q

What happens when an antigen binds to the antigen receptors on a lymphocyte?

A

The lymphocyte will start dividing.

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11
Q

Where do B cells develop?

A

Bone marrow.

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12
Q

Where do T cells develop?

A

Thymus.

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13
Q

At which stage in their development do lymphocytes move to the secondary lymph tissue?

A

Once they have succesfully expressed an antigen receptor on their surface and have been educated to weed out cells which recognise self molecules.

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14
Q

What is the structure of B cell receptor?

A

Immunologobulin formed of 2 identical heavy chains and 2 identical light chains.

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15
Q

What is the structure of the T cell receptor?

A

Two chains (α and β) of approximately equal size.

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16
Q

What is the difference between B and T cells in the way that they recognise antigens?

A

B cells use surface bound antibodies which recognise molecular shapes called epitopes that are present on intact molecules.

T cell receptors recognise fragments of antigens that are presented by other immune system cells.

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17
Q

What is the function of MHC molecules?

A

To present fragments of antigens to T cells.

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18
Q

How do T cells recognise that a cell is infected by a pathogen?

A

All cells sample their own internal proteins and place fragments of them on their cell wall. If a cell is infected, fragments of the pathogen’s proteins will also be expressed on the cell surface where they can be recognised by T cells.

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19
Q

Why is the immune response in the brain and spinal cord limited?

A

Because nerve cells are irreplaceable so it is better to live with damage to cells than to allow cytotoxic T cells to kill them. This is why nerve cells may remain chronically infected with viruses such as herpes.

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20
Q

Which CD marker is expressed by TC cells?

A

CD8.

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21
Q

Which CD marker is expressed by TH cells?

A

CD4.

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22
Q

What are the principle functions of TH cells?

A

TH1 - help phagocytes to destroy ingested pathogens.

TH2 - help B cells to make antibodies.

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23
Q

What are cytokines?

A

Generic term for secreted molecules produced by a wide variety of cells which act as signalling molecules.

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24
Q

Give some examples of cytokines.

A

Interleukins

Interferons

Chemokines

Tumour necrosis factors

Transforming growth factors

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25
Q

How do TH cells interact with phagocytes and B cells?

A

Signalling through cytokines.

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26
Q

What triggers a B cell to divide and differentiate into plasma cells?

A

Binding to an antigen and receiving the appropriate cytokine signals from a TH2 cell.

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27
Q

Where does the differentiation of B cells into plasma cells primarily take place?

A

Lymphoid tissues.

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28
Q

What do plasma cells produce?

A

Secreted form of antibody with an identical specificity to that of the original B cell, only lacking the part of the molecule that binds the antibody to the cell membrane.

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29
Q

What is the lifespan of a plasma cell?

A

A few weeks.

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30
Q

What is the function of Natural Killer cells (large granular lymphocytes)?

A

To kill tumour cells or cells which are infected by viruses.

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31
Q

What are the two main types of phagocyte?

A

Neutrophils and mononuclear phagocytes.

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32
Q

What are the three types of polymorphonuclear leukocytes? Describe their nucleus.

A

Neutrophils

Eosinophils

Basophils

The nucleus has several lobes.

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33
Q

What is the main function of neutrophils?

A

Antibacterial defence.

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34
Q

What is the main function of eosinophils?

A

Defence against parasitic worms.

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35
Q

What is the main function of basophils?

A

Control and development of inflammation.

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36
Q

Describe the lifestyle of neutrophils?

A

The make a one way trip from the bone marrow to the different tissues of the body and tend to congregate at sites of bacterial infection, being attracted by both the products released by bacteria and the cytokines released by immune system cells. They are a large component of pus.

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37
Q

What is the lifestyle of mononuclear phagocytes?

A

Some are mobile within tissues and other are fixed cells (e.g. Kupffer cells in liver).

Every tissue needs a permanent population of phagocytes to clear up debris and they may become activated in defense if the organ becomes infected.

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38
Q

How do macrophages develop?

A

Monocytes migrate out of blood vessels into tissues where they differentiate into macrophages.

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39
Q

What are the functions of macrophages?

A

Powerful killers of bacteria and parasites.

Antigen presentation to TH1 cells.

40
Q

Give two examples of antigen presentation.

A

Macrophages to TH1 cells >> activation of macrophage

B cells to TH2 cells >> differentiation of B cells

41
Q

What is the function of dendritic cells?

A

Antigen presentation to T cells, particularly naive T cells which have not previously been activated by antigen.

42
Q

Where are dendritic cells normally found?

A

Usually in lymphoid tissues, but also in blood and lymph.

43
Q

What are the functions of mast cells?

A

Induction of inflammation.

Attraction of leukocytes to a site of inflammation (chemotaxis).

44
Q

Where are mast cells normally found?

A

In tissue, close to blood vessels.

45
Q

What are the 5 classes of antibodies?

A

IgA

IgG

IgM

IgD

IgE

46
Q

What are the main features of IgA?

A

Main antibody in mucous secretions

Protects against infections of gut, respiratory tree and GU tract.

47
Q

What are the main features of IgG?

A

Main antibody in tissues and fluids

Directly neutralizes many toxic molecules

Prevents bacteria and viruses from attaching to cells

Acts as adapter molecule for phagocytes allowing them to recognize and internalize pathogens

Protection of foetus and newborn - only antibody to cross the placenta

48
Q

What are the main features of IgM

A

First antibody to be produced in immune response

49
Q

What are the main features of IgD?

A

Involved in activation of B cells

No major direct role in defence against pathogens

50
Q

What are the main features of IgE?

A

Development and control of inflammation

51
Q

What is the main immunoglobulin in mucous secretions?

A

IgA

52
Q

What is the main antibody in blood and tissue fluids?

A

IgG

53
Q

Which immunoglobulin protects against infections of the gut, respiratory tract and genitourinary tract?

A

IgA

54
Q

Which is the first immunoglobulin to be produced in an immune response?

A

IgM

55
Q

Which is the only immunoglobulin to cross the placenta?

A

IgG

56
Q

Which immunoglobulin is involved in control and development of inflammation?

A

IgE

57
Q

Which immunoglobulin is involved in the activation of B cells?

A

IgD

58
Q

Which immunoglobulin directly neutalizes toxic molecules and prevents bacteria and viruses from attaching to cells?

A

IgG

59
Q

What determines the class of an immunoglobulin?

A

The heavy chains.

60
Q

Which region of IgG antibodies forms the antigen binding site?

A

V domain of the Fab region

61
Q

Which region of an IgG antibody binds to leukocytes?

A

Fc region

62
Q

What is the significance of the hinge region of an antibody?

A

It gives the molecule flexibility allowing the two antigen binding sites to bind to two identical epitopes on the surface of a bacteria or virus.

63
Q

Which antibodies have 4 domains in their heavy chains?

A

IgG

64
Q

Which antibodies have 5 domains in their heavy chains?

A

IgM and IgE

65
Q

What is special about the structure of IgA and IgM

A

They are usually produced in polymeric form with IgA usually being dimeric and IgM usually being pentameric.

66
Q

What are the features of the attachment between antibody and epitope?

A

Complementary shapes

Many weak covalent bonds forming a strong binding

67
Q

What is antibody affinity?

A

How strong a bond an antibody makes to an epitope?

68
Q

Which antibodies tend to have low affinity?

A

IgM

69
Q

What is antibody avidity?

A

How many binding sites an antibody has?

70
Q

Why does IgM have high avidity?

A

Because it has 10 antibody binding sites allowing it to bind to clusters of epitopes on a pathogen’s surface.

71
Q

What is cross reactivity and when can it cause problems?

A

When different antigens share the same epitope. This can occur in auto-immune disease.

72
Q

What are primary and secondary antibody responses?

A

Primary refers to an individual’s first encounter with an antigen, secondary refers to further encounters with the same antigen.

73
Q

What is different in a secondary antibody response compared with the primary antibody response?

A

Lag time is reduced

Overall antibody level is higher

Antibodies persist for longer

Class switch from IgM production to IgG

Antibodies generally have higher affinity

74
Q

Why is vaccination effective?

A

Vaccination induces a mild primary response so that if the real pathogen is encountered a stronger secondary response will be initiated.

75
Q

What is opsonization?

A

The process by which a pathogen is tagged for phagocytosis

76
Q

How can a pathogen be opsonized?

A

Antibody opsonization - IgG

Acute phase proteins - C3b, CRP

77
Q

How can a phagocyte recognised a pathogen which has not been opsonized?

A

By specific molecules on its surface such as mannose - PAMP molecules. These are recognised by Pattern/Pathogen Recognition Receptors such as Toll Like Receptors, Lectin Receptors and Scavenger Receptors.

78
Q

Which cells make up the innate immune system?

A

Macrophages

Neutrophils

Mast Cells

Natural Killer Cells

79
Q

Which proteins make up the innate immune system?

A

Complement

Acute phase proteins

Cytokines

80
Q

Which cells make up the adaptive immune system?

A

B lymphocytes

T lymphocytes

81
Q

Which proteins are involved in the adaptive immune system?

A

Antibody

82
Q

What are the functions of phagocytes?

A

Initiation and amplification of inflammatory response

Scavenging of cellular and infectious debris

Ingesting microorganisms

Production of inflammatory molecules

Resolution and repair

83
Q

How do neutrophils reach the site of inflammatory stimulus?

A

Margination

Loss of intravascular fluid and increased plasma viscosity allows them to flow in the plasmatic zone, adjacent to the blood vessel wall of venules

Transmigration

They insert pseudopodia and transmigrate through the epithelium

84
Q

Which molecules increase leukocyte surface adhesion molecule?

A

C5a

Leukotreine B4

TNF

85
Q

Which molecules increase expression of endothelial cell adhesion molecules?

A

IL-1

Endotoxins

TNF

86
Q

What is chemotaxis?

A

Movement along a chemical concentration gradient

87
Q

Which compounds are chemotactic for neutrophils?

A

Bacterial product

Complement proteins

Cytokines

88
Q

What factors favour the resolution of acute inflammation?

A

Minimal cell death and tissue damage

Occurrence in an organ or tissue with regenerative capacity

Rapid destruction of causal agent

Rapid removal of fluid and debris by good local vascular drainage

89
Q

What factors favour the progression of acute to chronic inflammation?

A

Indigestible substances such as glass or suture material

Deep seated suppurative inflammation with inadequate drainage leads to abcess and granulation tissue

Recurrent episodes of acute inflammation & healing

90
Q

What are the predominant cells found in chronic inflammation?

A

Lymphocytes

Plasma Cells

Macrophages

Eosinphils

91
Q

Give some examples of primary chronic inflammation due to pathogens

A

TB

Leprosy

Brucellosis

Viral infections

92
Q

Give some examples of primary chronic inflammation that are not due to pathogens

A

Gout - foreign body reaction to endogenous material

Ulcerative colitis

Primary granulomatous disease, e.g. sarcoidosis

93
Q

What are the macroscopic appearances of chronic inflammation?

A

Chronic ulcer - breach of mucosa, base lined with granulation tissue, fibrous tissue extending to muscle layers

Chronic abcess cavity

Thickening of wall of hollow viscus by fibrous tissue

Granulomatous inflammation

Fibrosis

94
Q

What role do macrophages play in acute inflammation?

A

Appear late in acute inflammatory response

Phagocytosis - but less than neutrophils

Clear away tissue debris/damaged cells

May release lysosomal enzymes aiding digestion of inflammatory exudate

95
Q

What is a granuloma?

A

Aggregate of epitheliod histiocytes - macrophages of connective tissue with little phagocytic activity

96
Q
A

Disease Mechanisms (9 decks)

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