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Systems: Haematology + Immunology > Introduction to Immunology > Flashcards

Introduction to Immunology Flashcards

1
Q

What are the 3 components of immunity?

A
  • Physical barriers
  • Innate immunity
  • Adaptive immunity
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2
Q

What physical barriers are there?

A
  • Skin and epithelial mucosa
  • Secretions
  • Gastric acid
  • Normal flora
  • Physiological
  • Physical flushing of urinary tract
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3
Q

What secretions provide a barrier to infection?

A
  • Sweat
  • Tears
  • Gastric acid
  • Sebaceous glands
  • Mucous
  • Breast milk
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4
Q

What are the protective components of saliva?

A
  • Lysozyme: digests proteoglycan in bacterial walls
  • IgA: prevents attachment of microbes and may neutralise microbes insitu
  • IgG
  • Lactoferrin: sequesters free iron and has direct antimicrobial effects
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5
Q

How can commensal bacteria prevent infection?

A
  • Compete for nutrients
  • Prevent attachment
  • Release fatty acids and antibacterial proteins
  • Prevent invasion
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6
Q

What do lactobacilli in the vagina do?

A

Cause acidic pH (4-4.5)

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7
Q

What physiological responses prevent infection?

A
  • Temperature (fever)
  • pH
  • Location of immune cells within the bloodstream
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8
Q

Give examples of conditions where there is breached defences to infection.

A
  • Burns, xerostomia
  • Cystic fibrosis
  • C. difficile
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9
Q

Why can burns lead to infection?

A

Allow pathogens access and more optimal growing conditions

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10
Q

Why can CF lead to infection?

A

Increased viscosity of mucous reduces the ability of the cilia to clear infections allowing damage to the lungs to occur

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11
Q

Why can C.diff lead to infection?

A

Increase in bacteria due to abnormal flora which can lead to toxic megacolon

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12
Q

What cells are involved in the innate immune system?

A
  • Mast cells
  • NK cells
  • Basophils
  • Neutrophils
  • Eosinophils
  • Monocytes
  • Macrophages
  • Dendritic cells
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13
Q

What molecules are involved in the innate immune system?

A
  • Complement
  • Interferon
  • Cytokines
  • Acute phase reactants
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14
Q

What receptors are involved in the innate immune system?

A

Pattern recognition receptors

  • Toll like receptors
  • Mannan-binding lectin
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15
Q

What molecules are involved in the adaptive immune system?

A
  • Immunoglobulins

- Cytokines

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16
Q

What cells are involved in the adaptive immune system?

A
  • T cells

- B cells

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17
Q

What receptors are involved in the adaptive immune system?

A
  • T cell receptors
  • B cell receptors
  • MHC/HLA
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18
Q

What are the mechanisms of the innate immune system?

A
  • Inflammation
  • Recruitment of immune cells
  • Activation of complement
  • Opsonisation
  • Phagocytosis (and endocytosis)
  • NK cytotoxicity
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19
Q

What are the features of the innate immune system?

A
  • First line of defence
  • Rapid
  • Already present at birth
  • Some specificity
  • No memory – same response with re-exposure
  • Detects alteration from haemostasis
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20
Q

What do cytokines do?

A
  • Regulate the nature, duration and intensity of the immune response
  • Form a method of ‘communication’ between components of the immune system
  • Bind to specific receptors on target cells
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21
Q

What produces cytokines?

A

Predominantly macrophages and T cells

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22
Q

Give examples of pro-inflammatory cytokines.

A
  • TNF-a
  • IL-1
  • IL-6
  • Chemokines
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23
Q

What is involved in the inflammatory response?

A
  • Fever
  • Vasodilation
  • Recruit and activate other immune cells
  • Increase glucocorticoids leading to stress hyperglycaemia (also decrease in inflammatory response)
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24
Q

Give examples of anti-inflammatory cytokines.

A
  • IL-10

- TGF-B

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25
Q

What cytokines activate macrophages?

A

IFN-y

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26
Q

What cytokines activate eosinophils and mast cells?

A
  • IL-3
  • IL-4
  • IL-5
  • IL-13
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27
Q

What cytokines activate B cells?

A
  • IL-4
  • IL-5
  • IL-6
  • IL-21
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28
Q

What cytokines activate T cells?

A
  • IL-2
  • IL-4
  • IL-12
  • IFN-y
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29
Q

What cytokines act on bone marrow to increase leukocyte production?

A
  • Gm-CSF

- IL-3

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30
Q

What is inflammation a result of?

A

-Detection of foreign/breach in defences by pattern recognition receptors

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31
Q

What causes vasodilation?

A
  • Nitric oxide
  • Bradykinin
  • Prostaglandins
  • TNF-a
  • IL-1
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32
Q

What causes increased vascular permeability?

A
  • Nitric oxide
  • Leukotrienes
  • Histamine
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33
Q

What causes increased cell adhesion molecules?

A
  • TNF-a

- IL-1

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34
Q

What causes chemotaxis?

A

CXCL-8

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35
Q

What causes increased sensitivity to pain?

A

Bradykinin

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36
Q

What are the 3 complement pathways?

A
  • Classical
  • Lectin
  • Alternative
37
Q

What complement components are involved in chemotaxis of phagocytes to site of inflammation?

A

C3a

C5a

38
Q

What complement components are involved in opsonisation?

A

C3b

C4b

39
Q

What complement components are involved in lysis of micro-organisms?

A

C5b-9 complex

40
Q

What complement components are involved in maintaining solubility of Ag/Ab complexes?

A

C3b
C4b
C2

41
Q

What is opsonisation?

A

Preparing for eating

  • Reduces repellent negative cell charge
  • Increases no. of binding sites for phagocytes
42
Q

What are the main opsonins?

A
  • Complement C3b, C4b
  • Antibodies
  • Plasma proteins – mannose binding lectin
43
Q

Briefly describe phagocytosis.

A
  • Endocytosis
  • Enzyme destruction of pathogen
  • Exocytosis of waste products
  • Extracellular pathogens
44
Q

When does NK cytotoxicity occur?

A

If reduced MHC I expression leads to inhibition and destruction of cell

45
Q

What are the features of the adaptive immune system?

A
  • Specific
  • Delayed
  • Immunological memory
  • Faster responses to known antigen
46
Q

What are the divisions of the adaptive immune system?

A

Humoral

  • Antibody-mediated
  • B lymphocytes

Cell-mediated
-T lymphocytes

47
Q

Where do lymphocytes mature?

A
  • T cells in the bone marrow and thymus
  • B cells in the bone marrow
  • B and T cells then migrate to secondary lymphoid organs, where they encounter antigen
48
Q

Antigen

A

A molecule capable of inducing an immune response

49
Q

Antibody

A

A glycoprotein produced by B lymphocytes that binds antigens with a high degrees of specificity and affinity

50
Q

How do lymphocytes with diverse antigen binding sites arise?

A

Genetic changes

51
Q

How do T cells recognise antigens?

A

Require presentation of antigen via MHC

  • CD4+: MHCII
  • CD8+: MHCI (all nucleated cells and platelets)
52
Q

How do B cells recognise antigens?

A

Recognise antigen directly

53
Q

What type of pathogens do MHCI process?

A

Intracellular

54
Q

What type of pathogens do MHCII process?

A

Extracellular

55
Q

What central tolerance do T cells undergo?

A

In the thymus

  • Positive selection: can T cells recognise MHC?
  • Negative selection: does T cell interact too strongly with self-antigens via MHC?
56
Q

What central tolerance do B cells undergo?

A

In the bone marrow

-Self-reacting BCR

57
Q

What is peripheral tolerance?

A
  • Monitoring of lymphocytes within secondary lymphoid organs and circulation
  • Regulatory T cells recognise and destroy self-reactive lymphocytes
58
Q

What do cytotoxic T cells do?

A

Release IFN-y and TNF-a
-Direct anti-viral and anti-tumour effects

Release cytotoxic granules:
- Perforin + granzyme = apoptosis of target cell

Apoptosis also via:
-FasL-Fas interactions

59
Q

What is perforin induced apoptosis?

A
  • MHCI binds to CD8
  • Release of perforin and granzyme
  • perforin creates a pore in the cell membrane
  • Granzyme enters the cell and triggers apoptosis
60
Q

What do help T cells do?

A
  • Release cytokines to ‘help’ the activity of other immune cells
  • Promote B cell antibody class switching e.g. IgM to IgG
61
Q

What do Th1 cells do?

A

Intracellular pathogens

  • Maximise macrophage and CD8+ activity
  • Release IFN-γ
  • Inhibit TH2 response
62
Q

What do Th2 cells do?

A

Extracellular pathogens

  • Release IL-4, IL-5, IL-13
  • Activate mast cells, basophils, eosinophils
  • Class switching to IgE
  • Inhibit Th1 response
63
Q

What do Th17 cells do?

A

Extracellular pathogens

  • Pro-inflammatory
  • Recruit neutrophils and macrophages via CXCL-8
64
Q

What do regulatory T cells do?

A
  • Suppress CD4+ and CD8+ T cells
  • Control the response to self-antigens
  • Secrete IL-10 and TGF-β (anti-inflammatory and suppresses immune system)
65
Q

What does the FAB region of Ig bind to?

A

Antigen

66
Q

What does the Fc region of Ig bind to?

A

Communicates with immune cells

67
Q

What Ig is best at achieving complement?

A

IgM

68
Q

What Ig can cross the placenta?

A

IgG

69
Q

What Ig is contained in secretions?

A

IgA

70
Q

What Ig is involved in parasitic infections and allergy?

A

IgE

71
Q

How does antibody mediated immunity vary with time?

A

Immunity increases with each exposure

72
Q

What are the functions of antibodies?

A
  • Immune complex formation
  • Opsonisation
  • Activating the cascade complement (classical)
  • Antibody dependent cellular toxicity (ADCC) (bind to target cells and initiate a non-phagocytic cell-mediated destruction)
73
Q

What factor produces normal variation in immune function?

A

Age

74
Q

How does ageing affect immune function?

A

Elderly

  • Thymic involution
  • Fewer naïve T cells – dependent on memory T cells
  • Reduced ability for T cell expansion
  • Reduced B cell development and diversity (Diminished response to vaccination)
  • More dependent on innate immunity (But reduced function of pattern recognition receptors and superoxide killing)
75
Q

What cause secondary immune deficiency?

A

Environmental
-Malnutrition, trauma, burns

Disease
-Infection, diabetes, renal failure, asplenia, malignancy

Iatrogenic
-Splenectomy, drugs

76
Q

What drugs can cause immunodeficiency?

A
  • Immunosuppressant’s
  • Anti-rheumatics
  • Anti-epileptics
77
Q

Why is there immunodeficiency in HIV?

A

Virus binds to CD4+ cells to gain entry

  • T helper cells
  • Immune deficiency due to reduced CD4+ T helper cell function:
  • B cells, NK, CD8+, macrophage activity
78
Q

What proteins are affected in protein-calories malnutrition?

A
  • Cytokines
  • Acute phase reactants
  • Chemokines
79
Q

What is deficient in zinc malnutrition?

A
  • PMN
  • NK
  • Monocytes
  • B and T cells have impaired function
80
Q

What is deficient in iron malnutrition?

A
  • Enzymes within cellular function and metabolic pathways

- Impaired innate immune function

81
Q

What is zinc essential for?

A

Proliferating cells

82
Q

What is ciclosporin?

A

Calcineurin inhibitor: reduced inflammatory cytokine release from T cells-

83
Q

What does rituximab do?

A
  • Binds to CD20 (B lymphocytes)

- Allows NK and complement mediated apoptosis

84
Q

What do glucocorticoids do?

A

Anti-inflammatory

  • Activate lipocortins: reduce phospholipase A2 and arachidonic acid release
  • Alter transcription of enzymes needed for inflammation
85
Q

How are B cells activated by Th cells?

A
  • Anigen binds to B cell via BCR
  • MHCII detects extracellular pathogen and binds to Th which activates B cell

Leads to:

  • Proliferation of B cells
  • Production of memory B cells
  • Formation of plasma cells (production of free antibody specific to antigen)
  • Neutralisation
  • Opsonisation
86
Q

What triggers the classical complement pathway?

A

Immune complexes (Ab-Ag)

87
Q

What does the lectin complement pathway start with?

A

Mannose binding lectin

88
Q

What triggers the alternative complement pathway?

A

C3b directly binding to a microbe

Systems: Haematology + Immunology (19 decks)

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