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Immunology > L2&3 Cells of the Immune System > Flashcards

L2&3 Cells of the Immune System Flashcards

1
Q

What are the physical barriers in the immune system?

A

Skin & mucous membranes, Eye

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2
Q

What are the special characteristics of the skin?

A

Keratinised cells, shedding of cells, dryness, acidity (pH 5-6) & fatty acids (anti-bacterial function), normal skin microflora antagonistic to pathogens

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3
Q

What do epithelial cells in the eye secrete?

A

Mucus

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4
Q

What enzyme is present in tears, and what does it do?

A

Lysozyme - attacks the peptidoglycan layer in bacterial cell wall

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5
Q

Does the Omicron variant of COVID-19 tend to affect the upper or lower respiratory tract more?

A

Upper

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6
Q

What bacteria typically colonise the URT?

A

Staphylococcus, Streptococcus

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7
Q

What bacteria/viruses commonly infect the LRT?

A

Mycobacterium tuberculosis, Influenza A, COVID-19

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8
Q

What is the pH of the stomach?

A

pH 2

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9
Q

What are examples of food poisoning associated pathogens that can survive the acidity of the stomach?

A

Salmonella, Listeria

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10
Q

Which part of the GIT would you find Immunoglobulin A?

A

Small intestine

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11
Q

Does the large intestine mainly contain aerobic or anaerobic bacteria?

A

Anaerobic

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12
Q

What cells produce mucus, and what glycoprotein is found in mucus?

A

Goblet and mucus-secreting cells.

Mucin - glycoprotein

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13
Q

What is the function of enterocytes?

A

Absorb nutrients

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14
Q

Is the small intestine primarily an aerobic or anaerobic environment?

A

Aerobic

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15
Q

What are the 4 major Phyla in the human GIT?

A

Firmicutes (by far the most common) G+ e.g. Lactobacillus & Enterococcus
Bacteriodetes G- e.g. Bacteroides
Actinobacteria G+ e.g. Bifidobacterium spp.
Proteobacteria G- e.g. Escherichia, Salmonella, Vibrio

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16
Q

Does Streptococcus pneumoniae have a high, moderate or low virulence?

A

High

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17
Q

Examples of phagocytes in the innate immune system

A

Neutrophils, macrophages, dendritic cells

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18
Q

What are PRRs? Give an example

A

Pathogen Recognition Receptors

e.g. Toll-like receptors (TLRs)

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19
Q

What do PRRs recognise?

A

PAMPs = pathogen associated molecular patterns on pathogens (danger signals)

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20
Q

What PRR recognises LPS (a PAMP)?

A

Toll-like receptor 4 (TLR4)

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21
Q

What happens when a PRR is triggered?

A

Regulatory cytokines and Interferons are secreted

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22
Q

How do cells such as macrophages and DCs connect the innate to the adaptive immune system?

A

They act as Antigen Presenting Cells (APCs) - present processed antigens from killed pathogens to T cells (adaptive)

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23
Q

Are bacteria generally found within our cells?

A

No - they tend to adhere to body surface layers or are ‘free-floating’ in body fluids. An exception is M. tuberculosis in lung macrophages of TB patients!

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24
Q

Viruses are either…

A

Naked or enveloped

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25
Q

Naked (non-enveloped) viruses have a…

A

Capsid that surrounds the DNA/RNA

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26
Q

What is an example of a naked virus?

A

Norovirus (winter vomiting bug) - causes gastroenteritis

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27
Q

What is the envelope in enveloped viruses?

A

A lipid bilayer - acquired from the plasma membrane of an infected cell as the virus ‘buds’ away

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28
Q

What do innate immunity PRRs recognise?

A

The nucleic acid in either DNA or RNA

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29
Q

What type of virus is Rotavirus?

A

dsRNA

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30
Q

What are the vast majority of viruses?

A

dsDNA

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31
Q

How do viruses enter cells? (in one word)

A

Endocytosis

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32
Q

What do cell surface TLRs mainly detect?

A

Bacteria and fungi

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33
Q

How are bacteria & viruses in cytoplasm detected?

A

NLRs and RLRs

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34
Q

How are viruses in endosomes detected?

A

TLRs

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35
Q

What are the 2 main roles of the lymphatic system?

A
  1. Removal of interstitial fluid from tissues

2. Monitor for infection/tissue damage

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36
Q

What is lymph?

A

Clear to white fluid that contains leukocytes (WBCs)

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37
Q

How does lymph drain back into the bloodstream?

A

Left subclavian vein via the thoracic duct

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38
Q

How much lymph is returned to blood circulation per day?

A

4 litres!

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39
Q

How many leukocytes are produced per day?

A

Around 4x10¹¹

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40
Q

What make up 95% of circulating granulocytes?

A

Neutrophils

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41
Q

Are granulocytes short or long-lived?

A

Short lived (continuously produced), 2-3 days

42
Q

Main role of polymorphonuclear cells (PMNs) or granulocytes?

A

Phagocytosis of invading microorganisms and cellular debris

43
Q

Phagosomes (phagocytosed microbes contained within vacuoles) fuse with __ to form __

A

fuse with LYSOSOMES/GRANULES to form PHAGOLYSOSOMES

44
Q

What is CAP and what can it do?

A

CAP = cationic anti-microbial protein - can lyse & kill bacteria

45
Q

What are the 4 types of granules?

A
  1. Azurophilic (primary)
  2. Specific (secondary)
  3. Gelatinase (tertiary)
  4. Secretory
46
Q

What is the main target of eosinophils?

A

Parasitic worms

bind worm larvae coated with IgG and IgE antibodies

47
Q

Are mast cells found in circulation?

A

No

48
Q

What is released when mast cells degranulate?

A

Histamine and other inflammatory mediators

49
Q

When do monocytes become macrophages?

A

When they migrate into tissues

50
Q

What are the 2 main functions of macrophages?

A
  1. ‘Professional’ phagocytic macrophages, role to remove particulate antigens such as pathogens & dead/dying cells
  2. APCs present pathogen antigens to T cells
    VERY IMPORTANT IN IMMUNOSURVEILLANCE
51
Q

What is the shape of a monocyte nucleus?

A

Horseshoe-shaped nucleus

52
Q

Macrophages have prominent__ membrane-bound __

A

prominent ELECTRON-DENSE membrane-bound LYSOSOMES

53
Q

What do mannosyl-fucose receptors bind?

A

Sugars on surface of microbes

54
Q

What do Fc receptors bind?

A

Antibodies bound to pathogen - IgG, IgM, IgA

55
Q

What can CD14 receptors bind?

A

LPS

56
Q

What are Neutrophil Extracellular Traps (NETs)?

A

Networks of secreted extracellular fibres, composed of DNA & granule contents

57
Q

What anti-microbial proteins do NETs contain?

A

Neutrophil elastase, cathepsin G, histones/DNA

58
Q

What are the 2 main functions of NETs?

A
  1. Kill the bacteria

2. Act as a physical barrier that prevents the spread of the pathogen

59
Q

What is Suicidal NETosis?

A

The release of NETs result in neutrophil death, different to apoptosis or necrosis

60
Q

Free radicals react with __ in active sites and binding sites of __, including __, leading to the death of the microbe.

A

amino acids
proteins
enzymes

61
Q

What is one of the only pathogens known to survive the really tough environment formed by free radicals, and how?

A

M. tuberculosis - due to its thick cell wall

62
Q

What does TLR4 recognise?

A

LPS on the surface of Gram negative bacteria

63
Q

What does TLR5 recognise?

A

Flagellin on motile bacteria

64
Q

What do NODs recognise?

A

Bacterial peptidoglycan in cytoplasm of a cell

65
Q

TLR3, TLR7 and TLR9 are in the endosome - what do they recognise?

A

Viral genomes (DNA and RNA) in cells

66
Q

What does TLR7 detect?

A

ssRNA e.g. Influenza A virus

67
Q

What type of virus is Influenza A?

A

ssRNA

68
Q

What are the 2 main types of T cells involved in immunity?

A

T helper cells and cytotoxic T cells

69
Q

How does the adaptive immune system ‘see’ antigens?

A

In the form of short peptides from proteins (& carbohydrates/lipids to a lesser extent)

70
Q

T cells can only ‘see’ antigens when…

A

When a peptide is presented to its TCR by an APC (MHC I and II)

71
Q

What is the classical APC in skin?

A

Langerhans cell

72
Q

Where do DCs originate?

A

Bone marrow, then migrate throughout the body

73
Q

What are the 2 principal roles of DCs?

A
  1. Recognition of invading microbes by PPRs on DCs, leading to destruction of pathogen & production of proinflammatory cytokines, chemokines & Interferons
  2. Presentation of ‘bits’ (usually short peptides) of the pathogens ‘antigens’ to T cells
74
Q

What is a unique characteristic of dendritic cells?

A

They can cross-present

75
Q

To which cells do MHC 1 present?

A

CTLs (CD8+)

76
Q

To which cells do MHC 2 present?

A

Th cells (CD4+)

77
Q

What is the role of DCs in immune tolerance?

A

T cells that respond to DCs carrying self-peptides are destroyed in the thymus by negative selection

78
Q

What is the role of DCs in B cell memory?

A

DCs play a role in the maintenance of B cell recall responses

79
Q

What are plasmocytoid DCs (pDCs) a major source of?

A

Anti-viral cytokines and interferons

80
Q

Where are NK cells derived from, and what do they do?

A

Derived from lymphoid precursors in the bone marrow

Kill tumour cells & virus-infected cells

81
Q

Do NK cells possess a TCR?

A

No

82
Q

What do naive B cells have?

A

A surface antibody (BCR)

83
Q

What do plasma B cells do?

A

Secrete Ab into circulation

84
Q

What do antibodies mainly recognise?

A

Peptides & intact folded proteins

85
Q

Around how many BCRs are in a cell?

A

10⁵

86
Q

What are the two isotypes of BCR?

A

IgM (mainly) and IgD

87
Q

What happens to the B cell when its surface Ab detects its antigen?

A

The B cell differentiates into an antibody-secreting plasma cell

88
Q

Where is secretory IgA (sIgA) secreted?

A

onto mucosal surfaces

89
Q

What are the 5 antibody subclasses?

A

IgA, IgG, IgM, IgE, IgD

90
Q

Cell-lineage specific cell surface markers:

A

CD3 found on all T cells, CD19 found on B cells

91
Q

For what is CD19 being used as a potential target for monoclonal antibodies?

A

In certain leukaemias

92
Q

Maturation marker cell surface marker:

A

CD1 on T cells in thymus, not on T cells in circulation

93
Q

What can cells with different densities be separated by?

A

Density-gradient centrifugation
RBCs go down to the bottom
All lymphocytes in white area “buffy coat”
Using antibodies attached to magnetic beads

94
Q

What is FACS in Flow Cytometry?

A

Fluorescence-activated cell sorter

95
Q

What is the aim of haematopoietic stem cell transplantation?

A

To re-establish a patient’s immune system following cancer-related therapy

96
Q

What is CD34?

A

A transmembrane phospho-glycoprotein

97
Q

What is the main role of T cells?

A

To eliminate microbes that survive inside cells - mainly viruses but some bacteria like M. tuberculosis. Therefore, T cells recognise cell-associated but not ‘free’ antigens

98
Q

What cells are CD3 and CD4 positive?

A

T helper cells

99
Q

What cells are CD3 and CD8 positive?

A

Cytotoxic T cells (CTLs)

100
Q

What are the 2 main types of TCR on Th and CTLs?

A

αβTCR - on majority of T cells

γδTCR - on a minor population of circulating T cells, mainly on intestinal intraepithelial T cells

101
Q

What cells do NK cells kill?

A

Cells that do not express MHC molecules on their surface i.e. virus-infected cells, cancer cells

102
Q

Give examples of duality in the immune system

A
  • innate and adaptive
  • innate: phagocytes & APCs
  • adaptive: B cells & T cells
  • T cells: Th cells & CTLs
  • BCRs: heavy & light chain
  • TCRs: alpha-beta & gamma-delta
  • immunity to bacteria/fungi & immunity to viruses/cancer
  • recognition of ‘self’ and ‘non-self’

Immunology (10 decks)

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