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1.3 POM Immunology > Lymphocytes > Flashcards

Lymphocytes Flashcards

1
Q

What are the 2 types of immune response?

A
  1. Innate
  2. Adaptive
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2
Q

Which 2 cells are critical to the innate immune response?

A
  1. Neutrophils
  2. Macrophages
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3
Q

Which cells are critical to the adaptive immune response?

A

B and T lymphocytes

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4
Q

Why is the adaptive immune system needed?

A
  1. Clears infection (innate only contains it)
  2. Prevents reinfection
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5
Q

What do issues in adaptive immunity lead to?

A

Autoimmune diseases (eg. asthma and lupus)

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6
Q

What are the 5 main differences between the innate and adaptive immune system?

A

Innate
- quick
- no memory
- neutrophils and macrophages
- can recognise which pathogen (virus/bacteria etc)
- same everywhere in body

Adaptive
- slower
- memory
- lymphocytes
- specific to exact pathogenic organism
- specific to site of infection

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7
Q

Why is immunological memory so important?

A

Prevents reinfection

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8
Q

Why is the adaptive immune response to a primary infection slower? (2)

A
  1. Takes time to find specific lymphocyte
  2. Takes time to activate lymphocyte
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9
Q

Why is the adaptive immune response to a secondary infection faster? (2)

A
  1. Memory cells localised to where primary infection was —> quickly finds specific lymphocytes
  2. Memory cells are quickly activated
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10
Q

Which immune response is utilised for vaccinations?

A

Adaptive

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11
Q

Which adaptive immune response do T cells stimulate?

A

Cell-mediated

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12
Q

Which adaptive immune response do B cells stimulate?

A

Humoral

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13
Q

What are the 2 main roles of T cells in the cell mediated response?

A
  1. Produce cytokines (T-helper) —> help shape immune response
  2. Kill infected cell (cytotoxic T)
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14
Q

What is the main role of B cells in the humoral response?

A

Produce antibodies

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15
Q

How do T and B cells recognise pathogens?

A

T-cell receptors (TCRs)
B-cell receptor (BCRs)

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16
Q

What are the 2 important regions of TCRs and BCRs?

A
  1. Variable
  2. Constant
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17
Q

Where does the variable region of TCRs and BCRs lie?

A

Sticks out of cell

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18
Q

Where does the constant region of TCRs and BCRs lie?

A

Sticks into cell

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19
Q

What does the variable region of TCRs and BCRs do?

A

Recognise pathogen

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20
Q

What does the constant region of TCRs and BCRs do?

A

Activate its lymphocyte

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21
Q

How does the adaptive immune system recognise pathogens?

A

Antigens

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22
Q

What is an epitope?

A

Region of antigen which the lymphocyte receptor binds to

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23
Q

What to TCRs and BCRs bind to?

A

Epitope of antigen

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24
Q

What type of epitopes are recognised by T cells?

A

Linear —> recognises primary structure of epitope (10 amino acids)

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25
Q

What type of epitopes are recognised by B cell antibodies?

A

Structural —> recognises tertiary and quaternary structure of epitope

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26
Q

What is important about the lymphocytes interacting with an antigen?

A

Specific to antigen
- 1 lymphocyte to 1 antigen

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27
Q

What is stimulated when a lymphocyte receptor binds to its cognate antigen?

A

Clonal expansion

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28
Q

What is a cognate antigen?

A

The antigen that a lymphocyte has its specific response to

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29
Q

What is important about the cells produced by clonal selection?

A

Receptors are the same as the original lymphocyte’s

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30
Q

What is the issue that comes with the high specificity of the adaptive immune system?

A

Antigen diversity

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31
Q

How does the immune system deal with antigen diversity?

A

Huge repertoire of BCRs and antibodies

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32
Q

What would be the issue with the antigen receptor diversity and how is this overcome?

A
  • Too many BCRs and antibodies (10^15-10^20) need coding for than the number of genes we have (25,000)
  • Gene recombination
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33
Q

When are functional genes for antigen receptors generated?

A

During B lymphocyte development

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34
Q

What is each BCR chain encoded by?

A

Separate multigene families on different chromosomes

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35
Q

What are the 3 gene families that code for BCR receptor chains

A
  1. Kappa
  2. Lambda
  3. Heavy chain
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36
Q

What is immunoglobulin gene rearrangement?

A

Process of rearranging gene combinations and orientations to give a wider range of BCR and antibody proteins coded for

37
Q

What are the 2 gene segments for each BCR light chain in humans?

A
  1. V (variable)
  2. D (diversity)
  3. J (joining)
38
Q

What are the 2 gene segments for each BCR light chain in humans?

A
  1. V —> 40 different
  2. J —> 5 differenct
39
Q

What is the function of TCRs?

A

Recognise antigen fragments presented by other cells (eg. dendritic) in the context of MHC

40
Q

What type of signalling happens for a TCR to activate its T cells?

A

Enzyme-linked —> clustering

41
Q

What is MHC?

A

Major Histocompatibility Comples

42
Q

What are the 2 functions of MHC?

A
  1. Defining self and not self cells
  2. Present antigens to T cells
43
Q

What are the 2 types of MHC?

A

1 and 2

44
Q

Which cells is MHCI present in?

A

All nucleated cells

45
Q

Which cells is MHCII present in?

A

Professional APCs (eg. dendritic)

46
Q

Which 2 components make up MHCI?

A
  1. Variable alpha chain (3 subunits)
  2. Common beta chain (1 subunit)
47
Q

Which 2 components make up MHCII?

A
  1. Variable alpha (2 subunits)
  2. Variable beta (2 subunits)
48
Q

Which T cells does MHCII bind to?

A

CD4 (T-helper)

49
Q

Which T cells does MHCI bind to?

A

CD8 (cytotoxic T)

50
Q

What is the difference between the types of pathogens/antigens presented on MHCI vs MHCII?

A
  1. MHCI —> intracellular
  2. MHCII —> extracellular
51
Q

What are the 3 main differences between MHCI and MHCII?

A

MHCI
- Pathogen processed in cytosol
- Intracellular pathogens
- Presented to CD8 T-cells

MHCII
- Pathogen processed in endosomes
- Extracellular pathogens
- Presented to CD4 T-cells

52
Q

Which genes encode MHC proteins?

A

HLA genes

53
Q

Why are HLA genes polygenic?

A

3 different classes

54
Q

How many classes of HLA genes are there?

A

3

55
Q

What type of genetic expression occurs for HLA genes?

A

Co-dominant

56
Q

What is the maximum number of HLA genes a person can have and why?

A

6
- If heterozygous for at 3 classes of HLA genes

57
Q

What are the 2 types of T cells?

A
  1. T-helper cells (Th cells) —> CD4
  2. Cytotoxic T cells (CTLs) —> CD8
58
Q

Which APCs do T-helper 1 cells bind to?

A

Virus-infected cells

59
Q

Which APCs do T-helper 2 cells bind to? (2)

A
  1. Macrophages
  2. B-cell (antigen-specific)
60
Q

What chemicals do T-helper cells produce?

A

Cytokines

61
Q

What are cytokines?

A

Proteins/glycoproteins acting as signalling molecules in the immune system

62
Q

What are the 5 types of T-helper cell?

A
  1. Th1
  2. Th2
  3. Th17
  4. Treg (Th0)
  5. Tfh (follicular)
63
Q

What are the 2 functions of T-helper 1 cells?

A
  1. Pro-inflammatory
  2. Boost cellular immune response
64
Q

What are the 2 functions of T-helper 2 cells?

A
  1. Pro-inflammatory
  2. Control bacterial and fungal infections
65
Q

Which 3 cytokines are produced by T-helper 1 cells?

A
  1. IFN-γ
  2. TNF (tumour necrosis factor)
  3. IL-12
66
Q

Which 3 cytokines are produced by T-helper 2 cells?

A
  1. IL-17
  2. IL-6
  3. IL-23
    think 17 + 6 = 23
67
Q

Which 2 pathogens do T-helper 1 cells respond to?

A
  1. Viruses
  2. Intracellular bacteria
68
Q

Which 3 pathogens do T-helper 2 cells respond to?

A
  1. Helminth parasites
  2. Bacteria
  3. Fungi
69
Q

What are CTLs?

A

Cytotoxic T Lymphocytes

70
Q

What do CTLs do and how?

A

Kill infected cells
- Apoptosis

71
Q

What are stored in CTL cytotoxic granules? (3)

A
  1. Perforin —> holes in membrane
  2. Granzymes —> stimulate apoptosis
  3. Granulysin
72
Q

What happens when the CD8 of a CTL binds to the MHCI of a cognate pathogen?

A

Release chemicals in cytotoxic granules

73
Q

What are the 4 steps of how CTLs kill virus-infected cells?

A
  1. Virus infects cell —> cell displays non-self MHCI
  2. CD8 of TCR on CTL binds to MHCI of infected cell
  3. CTL activated —> releases chemicals in cytotoxic granules on infected cell
  4. Infected cell undergoes apoptosis —> killed
74
Q

What is the structure of an antibody? (5)

A
  1. Variable region (top half)
  2. Constant region (bottom half)
  3. 2 Heavy chains (long inner)
  4. 2 Light chains (short outer)
  5. 3 Disulfide bridges (between 2 heavy chain + between each heavy and long chain pair)
75
Q

What are the 3 roles of antibodies?

A
  1. Neutralisation —> covers binding sites of pathogen
  2. Opsonisation —> allows for macrophage phagocytosis
  3. Complement activation
76
Q

What are the 5 classes of antibody?

A
  1. IgG
  2. IgM
  3. IgA
  4. IgD
  5. IgE
77
Q

What is the shape of each 5 antibody class?

A
  • IgG —> normal (Good)
  • IgM —> 5 together (Mum likes flowers)
  • IgA —> short/2 together/3 together (Acrobatics)
  • IgD —> normal (gooD)
  • IgE —> normal but longer (Elongated)
78
Q

What is the function of each 5 antibody class?

A
  • IgG —> opsonisation and neutralisation (Good)
  • IgM —> first produced (Mum first before baby)
  • IgA —> in mucosal tissue
  • IgD —> ?
  • IgE —> allergy (Eosinophils and IgE)
79
Q

What are the 4 subclasses of IgG antibodies?

A

IgG1, IgG2, IgG3, IgG4

80
Q

When are the binding sites of a BCRs made?

A

Before cell ever encounters an antigen

81
Q

How many BCRs are on each B lymphocyte?

A

Thousands

82
Q

What do BCRs bind to?

A

Soluble antigens

83
Q

How are B cells activated? (2)

A

Accesory signals from…
1. Microbial consituents
2. T-helper cells

84
Q

What are the 2 pathways of antibody production by B cells?

A
  1. Thymus-independant (direct microbial constituents)
  2. Thymus-dependant (T-helper cells)
85
Q

What are the 3 differences between the thymus-dependant and thymus-independant antibody production?

A

Thymus-independant
- Direct microbial constituents activate B-cell
- IgM antibody production
- No memory

Thymus-dependant
- T-helper cells activate B-cell
- IgG production (all classes)
- Memory

86
Q

How does thymus-independant antibody production work?

A
  1. BCRs bind to antigens antigen often on polysaccharide (repeated structure) —> first signal
  2. Other receptors on B cell bind to PAMPs (Pathogen-Associated Molecular Patterns eg. LPS) —> second signal
87
Q

How does thymus-dependant antibody production work? (5)

A
  1. BCR recognises antigen —> binds
  2. Antigen internalised and degraded —> peptides
  3. Peptides associate with self MHCII —> expressed on surface
  4. T-helper cell binds to complex —> activates B cell
88
Q

Why does the innate immune response occur as well as adaptive immune response?

A

Adaptive system takes time —> innate buys time by containing the infection

1.3 POM Immunology (13 decks)

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