Adaptive immunity Flashcards

1
Q

Characteristics of adaptive immunity

A

Takes a longer time period to be activated
Specific
Highly specialised

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2
Q

Functions of adaptive immune system

A

Recognises non-self antigens
Generates specific response
Immunological memory

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3
Q

What are the three main cells in the adaptive immune system?

A

B cells
T cells
NK cell

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4
Q

What are cytokines?

A

Cell signalling molecules

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5
Q

Function of interleukins

A

Target leukocytes

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6
Q

Function of interferons

A

Antiviral response

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7
Q

Function of chemokines

A

Mediate chemotaxis

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8
Q

What are the 4 different ways in which cytokines can act?

A

Individually - autocrine
Individually - paracrine
Individually - endocrine
Together

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9
Q

What is an autocrine chemical?

A

Acts on cell releasing chemical

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10
Q

What is a paracrine chemical?

A

Targets nearby cell

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11
Q

What is an endocrine chemical?

A

Released into blood stream to target distant cells

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12
Q

Which cytokines activate t-cells?

A

IL-12
IL-2
IFN-gamma
TNF- alpha

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13
Q

Which cytokines stimulate antibody production?

A

IL-4
IL-5
IL-13

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14
Q

Which cytokines are anti-inflammatory?

A

IL-10

TGF-beta

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15
Q

Where are T cells produced?

A

Bone marrow

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16
Q

Where do T-cells mature?

A

Thymus

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17
Q

Where are T-cells activated?

A

Lymph node

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18
Q

What are CD4 cells?

A

Helper cells

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19
Q

What are CD8 cells?

A

Cytotoxic cells

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20
Q

Which three cells can activate helper T cells and why?

A

Dendritic cells, macrophages and B cells

They all have MCH II

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21
Q

How are T-helper cell activated?

A
  • CD4 t-cells activated by antigen presentation
  • Antigen presented to helper T cell by MHC II molecule on dendritic cell in lymph node
  • Second signal - co-stimulation
  • Third signal - cytokines released
  • All 3 signals = activated CD4 T-cell that specifically targets this pathogen
  • CD4 cell proliferates and clonally expands
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22
Q

What will MHC II bind to always?

A

CD4 helper cells

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23
Q

What is produced when a helper T cell is exposed to IL-12?

A

TH1

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24
Q

What is produced when a helper T cell is exposed to IL-4?

A

TH2

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25
Q

What is produced when a helper T cell is exposed to IL-1 beta and IL-6?

A

TH17

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26
Q

What is produced when a helper T cell is exposed to IL-10 and TGF-beta?

A

T reg cells

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27
Q

What do TH1 cells do?

A

Fight intracellular pathogens by releasing IFN-gamma and IL-2
Cell-mediated response

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28
Q

What are the two outcomes when TH1 cells are exposed to IFN-gamma?

A

B - cell and the plasma cell

Macrophage - activated macrophage

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29
Q

What are the two outcomes when TH1 cells are exposed to IFN-gamma and IL-2?

A

NK cell - activated NK cell

CD8 cell - cytotoxic T cell

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30
Q

What do TH2 cells do?

A

Defend against extracellular bacteria and parasites

Humoral response

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31
Q

What is produced when Th2 cells are exposed to Il-4?

A

Plasma cells

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32
Q

What is produced when TH2 cells are exposed to IL-4 and Il-13?

A

Alternatively activated macrophage

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33
Q

What is produced when TH2 cells are exposed to Il-3 and IL-5?

A

Eosinophils

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34
Q

What is produced when TH2 cells are exposed to IL-3 and IL-9?

A

Basophils

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35
Q

What do TH17 cells do?

A

Defend against some bacteria and fungi

Pro-inflammatory response

36
Q

What is produced when TH17 cells are exposed to Il-17?

A

Cytokines and chemokines lead to increased neutrophil production

37
Q

What do T-reg cells do?

A

‘Turn off’ immune system to return to normal state

Releases anti-inflammatory cytokines like IL-10 and tif-beta

38
Q

What do CD8 cells do?

A

Release perforin and granzymes to puncture holes in infected cell
Kill by Fas

39
Q

How do CD8 cells kill?

A
  • When activated, travels through blood to infection via chemotaxis
  • Infected cell has MHC I on surface to present to cytotoxic t-cell which kills cell
  • Can kill by Fas on viral cell binding to Fas ligand portion of CD8 cell - connection triggers cascade to cause apoptosis (death receptor signaling)
40
Q

How are CD8 cells activated?

A

Activated by dendritic cell entering lymph node and presenting antigen to MHC II to activate T-helper cells. This presents antigen via MHC I. CD8 requires MHC I signals, co-stimulatory molecule and IL-2 and IFN-gamma to be released from T-helper cells

41
Q

How do NK cells recognise pathogens?

A

PRR on surface

42
Q

What do NK cells do?

A

Activate macrophages

Kill pathogens similarly to CD8 cells

43
Q

Where do B-cells develop and mature?

A

Bone marrow

44
Q

What molecule are B-cell receptors made from?

A

Immunoglobins

45
Q

Process of B-cell editing

A

Challenged with self-peptides
If they recognise peptides, receptor editing occurs
If this is successful the B cell matures in periphery
If unsuccessful the B cell is anergia

46
Q

What does anergy mean?

A

Frozen - inactive

47
Q

What is receptor editing?

A

Re-arranging B-cell receptor to stop it recognising self-tissue

48
Q

What is isotope switching?

A

Cytokines from T-cells (TH2) tell B-cells which antibodies to produce

49
Q

What will all antibodies initially be?

A

IgM

50
Q

How is IgG produced?

A

TH2 exposed to Il-2/4/6 or IFN-gamma

51
Q

How is IgE produced?

A

Th2 exposed to Il-4

52
Q

How are B cells activated?

A
  • Requires CD4 to be activated initially
  • Antigen binds to B-cell receptor
  • B cell processes antigen, presents on MHC II molecule which is recognized by T-helper cell
  • T-helper cell recognizes that B-cell knows what infection is being fought and creates antibodies
  • 3 signals and release of cytokines
  • Activates B-cell
  • Clonally expands (IL-2 and IL-5)
  • Differentiates into plasma cell (antibody production) or memory B-cell
53
Q

What are the 4 chains in an antibody?

A

2 heavy and 2 light

54
Q

Where is the antibody binding region on an antibody and what is it called?

A

At the top of the Y and variable region

55
Q

What is the constant region of an antibody?

A

The stalk

56
Q

What does the constant region of an antibody do?

A

Binds to cell membranes and starts complement cascade
Starts phagocytosis
Initiates cytotoxicity

57
Q

What are the 5 classes of antibodies?

A

IgD, IgM, IgG, IgA, IgE

58
Q

Characteristics of IgM

A

First antibody produced
Bind up to 10 antigen
Lower affinity to antigen
Good at opposing/neutralising pathogens

59
Q

Characteristics of IgG

A

Most abundant
High affinity to antigen
Neutralise pathogens/activate inflammation

60
Q

Characteristics of IgA

A

Secretory antibody found in secretory surfaces

Neutralise pathogens

61
Q

Characteristics of IgE

A

Largest antibody
causes mast cells to granulate
Fights parasitic infection and allergies

62
Q

What is opsonisation?

A

Antibodies bind to pathogen to highlight it to phagocyte

63
Q

How is the complement cascade activated?

A

Inflammation and activation of mast cells

64
Q

Process of cytotoxicity

A

Cytotoxic T cells and NK cells bind to antibody

Release enzymes and perforating granzymes to cause apoptosis

65
Q

Where is IgM found?

A

Blood

66
Q

Where is IgG found?

A

Blood, from mother to fetes, extravascular tissues

67
Q

Where is IgA found?

A

Milk
Lungs and airways
Intestines
Urogenital tract

68
Q

Where is IgE found?

A

Connective tissue mast cells

69
Q

What is the passive immune response?

A

Antibodies are given to us to fight pathogens

70
Q

What is the active immune response?

A

Body is creating antibodies

71
Q

What is natural passive response?

A

Placental transfer of antibodies

IgA in breast milk

72
Q

What is artificial passive response?

A

Injection of immunoglobulin

73
Q

What is natural active response?

A

Infection and resistance to re-infection

74
Q

Where do memory cells wait until re-infection?

A

Lymph nodes

75
Q

What are long-lived plasma cells?

A

Remaining after infection has been fought, continually secreting antibodies for quick response in future

76
Q

What is sub-clinical re-infection?

A

Repeatedly getting infections and mounting immune response in clearing infection. We don’t get any symptoms because immune system is always getting topped up. Forms constant reservoir of antibodies

77
Q

Why is it beneficial to test for t-cell tolerance?

A

Stops them attacking self tissue

78
Q

What happens if a t-cell binds to self tissue?

A

Apoptosed

79
Q

What happens to functioning t-cells?

A

Released in periphery to lymph node

80
Q

Where does t-cell tolerance occur?

A

Thymus

81
Q

When will T-cells undergo positive selection?

A

When they can’t bond to MHC

82
Q

When are cytotoxic T cells produced?

A

Weak affinity to peptide and MHC I-CD8 cells

83
Q

When are helper T cells produced?

A

Weak affinity to MHC II-CD4 cells

84
Q

What is the aim of T-cell tolerance?

A

Turn them single positive

85
Q

What is negative selection of T cells?

A

T-cells challenged by medullary epithelial cells. Medullary epithelial cells can produce proteins form any area of body. They produce lots of self peptides and display those to T-cells

86
Q

Where does negative T-cell selection take place?

A

Medella

87
Q

Process of T-cell tolerance

A

T-cells interact with DCs. They recognise peptide-MHC complexes with medium or high affinity undergo apoptosis (negative selection)
- Weak affinity to peptide and MHC I-CD8 cells - cytotoxic T cells
- Weak affinity to peptide and MHC II-CD4 cells = helper T cells
Initially double negative but converted to double positive (both CD4 and CD8 on surface)