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Immunity Flashcards

1
Q

What is CD?

A

Cluster differentiation - way of labelling

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2
Q

How do cells signal?

A

Signalling though surface molecules or signalling through secreted molecules

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3
Q

What is the dark side to the immune system?

A
  • Allergy (immunity to non harmful things)
  • Autoimmunity (immune system attacking the body)
  • Rejection of transplants
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4
Q

What are the mechanisms of preventing infection?

A

Barriers. Innante immune system. Adaptive immune system.

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5
Q

How do barriers prevent infection?

A

Skin, respiratory and digestive tracts. Physical - epithelial. Chemical - saliva/mucus.

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6
Q

How does the innate immune system prevent infection?

A

Fast. Invariant receptors. Broad specificity, No memory. Eg neutrophils, macrophages, dendrite.

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7
Q

How does the adaptive immune system prevent infection?

A

Slow. Highly variant receptors. Highly specific. Generates memory. T cells and B cells.

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8
Q

Where are stem cells produced?

A

Bone marrow

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9
Q

Where do immune cells develop?

A

In primary lymphoid organs

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10
Q

How do immune cells travel through the body>

A

Migrate via lymph and blood to specialised lymphoid organs. From periphery to lymph nodes. Here response occurs.

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11
Q

What are secondary lymphoid organs?

A

Defined structure that promote adaptive immune response

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12
Q

What are the main stages of immunity?

A
  1. Recognition (innate then adaptive)
  2. Effector response (innate and adaptive)
  3. Memory (adaptive only)
  4. Immune turn off = immune regulation
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13
Q

What is recognition?

A

Immune cells distinguish Self (dont kill) and Non-Self (kill)

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14
Q

What are PAMPs?

A

Pathogen associated molecular patterns - pathogens have evolutionary conserved molecules

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15
Q

What are PRRs?

A

Patter recognition patter receptors to recognise PAMPs

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16
Q

Describe recognition in a gram -ve bacter.

A
  • LRS = PAMP
  • TLR4 = PRR
  • LPS binds to TLR4
  • Results in inactivation
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17
Q

What can innate immune cells do?

A

Express multiple PRR at the same time

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18
Q

Describe the activation of a macrophage?

A
  • Professional phagocyte
  • Kills bacteria
  • Recruits other immune cells = inflammation (neutrophils, cyotkines, chemokines)
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19
Q

Describe the activation of a dendritic cell.

A
  • Phagocytes
  • Antigen presenting cell = APC
  • Takes up pathogen proteins
  • Migrates to secondary lymphoid organs
  • ‘Presents’ fragments of pathogen proteins → sticks on surface
  • Activates T cells
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20
Q

What is an example of a primary lymphoid?

A

Thymus, bone marrow

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21
Q

What is an example of a secondary lymphoid?

A

Spleen, lymph node

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22
Q

Which two ways can antibodies protect against pathogens?

A
  1. Direct neutralisation of toxins
  2. Pathogen opsonisation and uptake by phagocyte
  3. Complement activation
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23
Q

How do epitopes recognised by T cells and B cells differ?

A

T cells can recognise only linear eptitopes. B cells can recognise both linear and conformational epitopes.

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24
Q

What are the main cells of the adaptive immune response?

A

Dendritic cells (activation of the adaptive immune system), T cells and B cells

25
What are lymphocytes?
T cells and B cells
26
What are CD4 Th cells?
Helpers
27
What are CD8 Tc cells?
Cytotoxic cells - killers
28
What are T and B cells activated through?
Surface receptors eg BCR and TCR
29
Compare BCR and TCR
Made in a similar fashion but of completely different proteins
30
Describe the BCR
Membrane bound antibody with the same specificity as secreted antibody
31
What are antigens?
Pathogen molecules recognised by T or B cells
32
What do T cells recognise?
Protein
33
WHat do B cells recognise?
Proteins, sugars and lipids
34
What is an epitope?
Specific part of the antigen that binds to the BCR or TCR
35
What are the forms of epitopes?
Linear or conformational
36
What does the B cell recognise?
Conformational and linear shapes
37
What does the T cell recognise?
Linear
38
What is a conformational epitope?
Parts of the amino acid only brought together when the protein folds
39
WHat is the linear epitope?
Stretches of amino acid that exist in the primary sequence
40
Describe clonal selection of lymphocytes.
1. Each lymphocyte has multiple copies of single antigen receptor 2. Antigen binding causes cell activation and clonal expansion 3. All daughter cells have the same antigen receptor specificity
41
What happens in the secondary lymphoid organ?
- Antigen can directly bind to BCR on surface of B cells | - T cells only binds to antigens that are present to them
42
Describe the bind of BCR and antigen
BCR is a surface antibody Antibody can bind directly to intact targets (antigens) B cells can bind linear and conformational epitopes
43
How are B cells activated?
1. Lymphatic drains to lymph node 2. Pathogens can migrate directly into lymph node 3. Pathogen molecules interact with B cells 4. Binds to BCR and activates it 5. Get clonal expansion 6. Secrete antibodies and bind to the pathogen molecules
44
What are the specific zones of lymph nodes?
T zone and B zone
45
WHat do antibodies do?
- Antibody directly neutralises pathogen molecule eg toxin | - Antibody ‘opsonises’ pathogens increasing phagocytes
46
What is meant by 'opsonises'?
innate immune cells express Fc receptors = FcR, can then phagocytose the whole complex
47
What is the structure of an antibody?
``` variable = Fab portion → provides the specificity non-variable= Fc portion ```
48
How are T cells activated?
1. TCR binds to an antigen binds to a peptide present by MHC proteins 2. T cell receptor recognises the peptide and MHC molecule 3. The peptide is the antigen for the T cell 4. Activation
49
What are the Differences in antigen presentation to CD8 Tc and CD4 Th cells?
1. Type of cell that present antigenic peptide 2. MHC molecule that present peptide (MHC I or MHC II) 3. Where antigen comes from (cytosol vs extracellular) 4. Consequences of T cell activation (kill or help)
50
How are CD8 Tc Cells activated?
- Destroy infected cells - Host and viral proteins degraded by proteases - host and viral peptides - viral peptide on MHC class I - recognised by CD8 Tc cell - interaction is stabilised by a co-receptor called the CD8 protein - results in activation
51
What happens with MHC class I in normal cells?
- All cells constantly display a sample of their proteins in the form of peptides which are always bound to MHC class I - Host proteins constantly being degraded by host proteases - Create host peptides and are displayed in MHC class I
52
How are CD4 Th cells activated?
- a dendritic cell → draining lymph node T zone and interacts with the CD4 Th cells - Dendritic cells forms a lot of contacts with the CD4 T cell which activates it - Dendritic cells present antigenic peptides on their surface using MHC class II - These peptides derive from extracellular pathogens CD4 protein is co-receptor for MHC II and stabilised and activates the T cells ‘helps’
53
What does CD4 do?
'help’ B cell antibody production | ‘help’ macrophages kill pathogens
54
How do CD4 cells 'help’ B cell antibody production
through production of cytokines or surface molecules result in the B cell producing higher affinity antibodies and go through class switching
55
How do CD4 cells ‘help’ macrophages kill pathogens?
activated, producing cytokines which increase production anti-microbial factors with better microbial killing
56
What is the diversity problem?
Adaptive immune systems requires a lot of specific B and T cells for the endless number of pathogens. B and T cells need to be highly specific to avoid autoimmunity
57
What is generation of diversity in TCR?
TCR → 2 long polypeptides with and alpha chain and a beta chain → within the chains there is a variable and a constant region Gene rearrangement Genes for TCR and BCR encoded in gene segments Each segment of variable region has many different variants Gene segments brought together through random gene rearrangement → random variant genes are brought together – alpha genes has 5000 variants, beta genes has 1000 variants Any alpha chain can potentially combine with any beta chain
58
How many receptors are there in the adaptive immune system?
10^18

Microbiology (8 decks)

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