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Biomedicine > Immune System 15 > Flashcards

Immune System 15 Flashcards

1
Q

What is the immune system?

A

A versatile defence system that protects us from pathogenic microbes

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2
Q

Facts about the first line of defence

A

Innate immunity
Physical barrier created by the skin and mucous membranes

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3
Q

Facts about the second line of defence

A

Innate immunity
Non-specific immune response that includes immune cells, proteins, fever and inflammation

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4
Q

Facts about the third line of defence

A

Specific / adaptive immunity
Activated by innate immune system
Specific response to a specific pathogen

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5
Q

What is a pathogen

A

An infectious agent that can cause disease in a host

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6
Q

How can pathogens enter the body?

A

Breaks in the skin
The respiratory system
The digestive system
Reproductive system
Eyes

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7
Q

What is an antigen

A

A substance that can be recognised by leukocytes

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8
Q

What are the two types of antigen

A

Foreign antigens
Self-antigens

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9
Q

What are antigens normally made from

A

Proteins

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10
Q

What are antibodies

A

Proteins that are produced in response to a specific antigen. They combine with these specific antigens

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11
Q

What are the two main first lines of defence?

A
  1. the skin
  2. mucus membranes
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12
Q

How is the skin a first line of defence?

A

It’s a physical barrier with layers of tightly-packed epithelial cells.

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13
Q

What accessory structures does the dermis contain that have an immenue function

A

Sweat glands
Sebaceous glands

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14
Q

What is the immune function of sweat

A

Removes microbes from skin
Contains IgA

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15
Q

What is the immune function of sebum?

A

Contains fatty acids that inhibit microbial growth

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16
Q

Where do you find mucus membranes?

A

In the digestive, respiratory and urogenital tracts plus the conjunctive in the eyes

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17
Q

What washes away secretions in the mucus membranes?

A

Saliva, tears and mucus secretions

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18
Q

What is the mucociliary escalator and where is in found?

A

In the respiratory tract
Cilia propel foreign substances towards the pharynx where they are swallowed

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19
Q

How does the nose defend against pathogens?

A

Hairs filter air

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20
Q

How does the vagina protect against pathogens

A

It’s acidic

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21
Q

How does the gastric tract protect against pathogens

A

Acidity
Microflora outcompete pathogens
Excretion of urine and faeces expels microbes
Vomiting and diarrhoea are rapid means of expelling pathogens

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22
Q

When pathogens penetrate the physical and chemical barriers what do they encounter next?

A

The second line of defence

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23
Q

List some elements of the second line of defence?

A

Complement system
Transferrins
Phagocytes
Natural killer cells
Inflammation
Cytokines - eg interferons
Fever

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24
Q

What are transferrins and how do they work?

A

Iron-binding proteins in the blood - inhibit the growth of certain bacteria by reducing the amount of available iron.

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25
Q

What is the complement system and where is it made?

A

A defense system of over 30 proteins made by the liver

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26
Q

What happens when complement proteins are activated?

A

They act in a cascade (they are amplified)

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27
Q

What is the most common mechanism that complement proteins are activated?

A

‘Classical pathway’ where antigen-antibody complexes are formed

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28
Q

What are the three stages for complement proteins to destroy microbes?

A
  1. promote phagocytosis - coat microbes in a process called opsonisation which promotes the attachment of a phagocyte to a microbe
  2. promote inflammation - bind to mast cells to release histamine
  3. cause cytolysis by destroying microbes
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29
Q

What is opsonisation

A

In the complement system when a fragrame coats a microbe to promote the attachment of a phagocyte to the microbe

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30
Q

What are cytokines?

A

Small protein hormones that stimulate or inhibit normal cell function

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31
Q

What are cytokines secreted by?

A

Leukocytes

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32
Q

Name three types of cytokines

A

Interleukins
Interferons
Tumour necrosis factor

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33
Q

What do interleukins do?

A

Mediators between leukocytes - mostly produced by T-helper cells

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34
Q

What do interferons do?

A

Involved in anti-viral responses

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35
Q

What does tumour necrosis factor do?

A

Promotes accumulation of neutrophils and macrophages to cause cell death

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36
Q

How do interferons work?

A

They interfere with viral replication
Attach and penetrate a cost cell to prevent it replicating

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37
Q

What is phagocytosis

A

Cell digestion

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38
Q

What attracts phagocytic cells to sites of inflammation

A

Chemotaxis

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39
Q

2 major types of phagocytes?

A

Macrophages (monocytes in blodd) and neutrophils

40
Q

Are phagocytes selective

A

no

41
Q

What type of phagocyte is also an antigen presenting cell?

A

Macrophages

42
Q

Two types of macrophages

A

Wandering and fixed

43
Q

Where can you find fixed macrophages?

A

Histiocytes
Kupffer cells
Alveolar
Microglia - nervous tissue
Langerhands - skin
Tissue macrophages - spleen, bone marrow and lymph nodes

44
Q

5 stages of phogocytosis

A
  1. chemotaxis - release chemicals to activate complement and attract phagocytes
  2. Adherence - of phagocyte to target
  3. Ingestion - engulf microbe
  4. Digestion - lysozymes and digestive enzymes
  5. Excretion - of indigestible material
45
Q

What are natural killer cells

A

Non-specific lymphocytes
The account for 5-10% of lymphocytes

46
Q

Where do you find natural killer cells

A

Blood, lymph nodes, spleen and bone marrow

47
Q

What do natural killer cells do?

A

They attack anything they don’t recognise

48
Q

How do natural killer cells perform phagocytosis?

A

Realease granules called perforin
Perforin inserts into the cell membrane and create a channel for tissue fluid which causes
cytolysis

49
Q

What is inflammation

A

A non-specific defensive response to tissue damage

50
Q

What can cause inflammation?

A

Pathogens, abrasions, chemicals, cell distortion, extreme temperature

51
Q

Is inflammation specific

A

No - it’s non-specific so the response to different insults is the same

52
Q

What are the five cardinal signs of inflammation

A

Redness
heat
pain
swelling
loss of function

53
Q

What are the first stage of inflammation

A
  1. vasodilation and increased permeability - allows additional blood to the area
    Increased permeability permits movement of immune cells
    Together these create redness, swelling and heat.
54
Q

Why does inflammation create pain

A

Pain is the result of injury from neurons and toxic chemicals

55
Q

What is the second stage of inflammation

A

Emigration of phagocytes (via chemotaxis)
Neutrophils squeeze through vessal wall
Monocytes follow
Dead phagocytes accumulate as puss

56
Q

What is stage three of inflammation

A

Tissue repair

57
Q

What do inflammatory mediators do?

A

Coordinate the inflammatory response

58
Q

4 inflammatory mediators

A

Histamine
Leukotrienes
Kinins
Prostaglandins

59
Q

Where does histamine come from and what does it do?

A

Released by mast cells and basphils - causes vasodilation and increased permeability

60
Q

Where do leukotrienes come from and what do they do?

A

Released by basophils and mast cells.
Attract phagocytes and increase vessel permeability

61
Q

What are kinins and what do they do?

A

Proteins that induce vasodilation and increased permeability

62
Q

What are prostaglandins and what do they do?

A

Lipids from damaged cells
Enhance effects of histamine and kinins - intensify pain

63
Q

What are the benefits of inflammation x 4

A

Promotes phagocytosis
Promotes immune response
Dilutes toxins
Fibrin formation - helps bind wounds

64
Q

Harmful effects of inflammation x 4

A

Swelling
Pain
Adhesions and scar tissue
Atherosclerosis

65
Q

4 possible outcomes of inflammation

A
  1. resolutions
  2. chronic inflammation
  3. granuloma - cellular attempt to contain foreign body
  4. fibrosis - scar tissue formation
66
Q

What is a fever

A

Abnormally high body temperature

67
Q

Why happens in the body when you get a fever

A

Hypothalamus thermostat is reset
Many bacterial toxins elevate body temperature - release fever causing cytokines such as interleukin-1
Interleukin-1 induces a fever

68
Q

What does an elevated body temperature do?

A

Makes interferons more effective
Inhibits growth of some microbes
Speeds up reactions that aid repair

69
Q

6 leukocytes

A
  1. Basophils and mast cells
  2. eosinophils
  3. neutrophils
  4. monocytes and macrophages
  5. natural killer cells
  6. B and T lymphocytes
70
Q

Facts about basophils and mast cells

A

In blood basophils
in blood mast cells
Release histamine - vasodilates and heparin
Receptors for IgE

71
Q

Facts about Eosinophils

A

Destroy parasitic worms via phagocytosis

72
Q

Facts about Neutrophils

A

60% of leukocytes
Phagocytic
Granules release lysozymes that digest debris

73
Q

Facts about monocytes and macrophages

A

Blood monocytes
Tissue - macrophages
Phyagocytic and secrete cytokines e.g interleukin-1 and TNF

74
Q

Facts about natural killer cells

A

Target foreign cells, secrete perforin to induce cytolysis

75
Q

B and T lymphocytes

A

Adaptive (specific) immunity and immunological memory

76
Q

What can B and T lymphocytes do as part of the third line of defence?

A

Possess specificity for antigen - recognise self from non-self
Produce immune memory
Allows quicker and more effective attack with next encounter

77
Q

What are cytokines?

A

Messenger molecules that mediate the connection between innate immune system and adaptive immune system

78
Q

What are the effector cells of the adaptive immune system?

A

T and B lymphocytes

79
Q

What does MHC stand for?

A

Major histocompatibility complex

80
Q

What are major histocompatibility complexes?

A

Group of cell-surface proteins that allow the immune system to differentiate healthy body cells from non-self

81
Q

What is the structure of major histocompatibility complex

A

4 polypeptide chains
Display a protein produced by the cell

82
Q

What is major histocompatibility complex I

A

Located in all body cells except erythrocytes
Abnormal proteins mix with MHC-I to display flags on the cell surface

83
Q

What is major histocompatibility complex II

A

Located only on the cell membrane of antigen presenting cells - macrophages and B-lymphocytes

84
Q

What does major histocompatibility complex II present antigens to?

A

T-helper cells

85
Q

What do T lymphocytes do?

A

Each t-lymphocyte has a unique t-cell receptor that only recognises a specific antigen

86
Q

Where are T lymphocytes produced and where do they mature?

A

Produced in bone marrow
Mature in thymus

87
Q

What are the two types of T-cell?

A

T-helper cells
Cytotoxic t-cells

88
Q

What are t-helper cells also known as?

A

CD4 cells

89
Q

What are cytotoxic t-cells also known as

A

CD8 cells

89
Q

What to traits must t-cells have?

A

Self-recognition and self-tolerance

90
Q

What does loss of self-tolerance lead to?

A

Autoimmunity

91
Q

What is adaptive immunity

A

Body’s ability to defend itself against specific agents

92
Q

What are the two types of adaptive immunity

A

cell-mediated and anti-body mediated

93
Q

Facts about cell-mediated immunity

A

By t-lymphocytes
Cytotoxic t-cells attack antigens
Mostly against intra-cellular pathogens

94
Q

Facts about anitbody-mediated immunity

A

By B-lymphocytes
Secrete specific antibodies
Mostly defend against extra-cellular pathogens

Biomedicine (20 decks)

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