Adaptive immunity Flashcards

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1
Q

Describe the overview of the adaptive response roughly

A
  1. infection
  2. transport of antigen to lymphoid organs
  3. recognition by native T and B cells
  4. clonal expansion and differentiation to effector cells
  5. removal of infectious agent
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2
Q

Why is the adaptive response advantageous?

A
  • generation time for bacteria can only take 20 mins and our generation time is 20 years
  • rapid evolution of pathogens means that new receptors will be required continuously
  • to compete, new receptors are continuously generated as lymphocytes develop in the bone marrow and thymus
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3
Q

What is an antigen?

A

any molecule that is specifically recognised by either T cell receptors (TCR) or antibodies

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4
Q

What is an epitope?

A

the site on an antigen that directly binds to an antibody or TCR

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5
Q

what is a T cell antigen?

A

peptide derived from an antigenic protein

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6
Q

What is a B cell antigen?

A

Proteins, carbohydrates

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7
Q

What is an antibody made up of and where does the antigen bind?

A
  • variable region (antigen binding site)

- constant region

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8
Q

How is the structure of the variable region decided?

A
  • in the germ-line DNA there are small segments of DNA in groups V,J and D
  • bone marrow cell will randomly select one V, D and J segment which will form the gene that determines the variable region
  • this is how diversity is created, by random gene recombination
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9
Q

What happens to newly produced B and T cells?

A

they are constantly recirculated through lymph nodes, lymphatic vessels and blood which improves the likelihood of encounter of a rare antigen specific cells with the antigen

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10
Q

What type of antibodies are produced at the start of an immune response and why?

A
  • IgM antibodies because they are pentameric so have 10 binding sites
  • low affinity
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11
Q

What types of antibodies due you produce later on in the immune response?

A
  • IgA (secreted to mucous membranes)
  • IgD (membrane receptor)
  • IgE (Localised on Mast cells)
  • IgG (highest concentration in serum)
  • smaller molecules (find it easier to move into tissue)
  • more specific
  • all have different roles
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12
Q

In terms of antibodies, what happens when a B cell differentiates into a plasma cell?

A

-lots of antibodies are released over a long period of time

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13
Q

What are the functions of antibodies?

A
  • neutralisation (prevent bacterial adherence)
  • opsonisation (promotes phagocytosis)
  • complement activation (antibody activates complement which enhances opsonisation and lyses some bacteria)
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14
Q

Where do T cells differentiate?

A

in the thymus gland

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15
Q

How are naive T cells produced?

A
  • T cell precursor leaves bone marrow and does into the thymus gland
  • in the thymus gland the cells proliferate and undergo TCR gene rearrangement
  • selection occurs (removal of self-reactive cells)
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16
Q

What cell type presents antigens to T cells?

A

Dendritic Cell

17
Q

How do dendritic cells transport the antigens ti lymph nodes?

A
  1. immature dendritic class reside in peripheral tissues
  2. dendritic cells migrate via lymphatic vessels to regional lymph nodes
  3. mature dendritic cells activate naive T cells in the lymphoid organs such as lymph nodes
18
Q

When is the only time that TCR will recognise antigens?

A

if they are presented on MHC proteins

19
Q

How does antigen presentation occur?

A
  1. the epitopes recognised by T cell receptors are often buried
  2. the antigen must first be broken down into peptide fragments
  3. the epitope peptide binds to a self MHC molecule
  4. the T cell receptor binds to a complex of MHC molecule and epitope peptide
20
Q

What will CD4+ T cells recognise?

A

exogenous peptides bound to MHCII proteins

21
Q

What is the consequence of CD4+ T cell recognising an antigen?

A

production of cytokines

22
Q

What is the role of Th1?

A

provides help signals for macrophages

23
Q

What is the role of Th2?

A

help signals to B cells, in particular for production of IgE

24
Q

What is the role of Th17?

A

inflammation

25
Q

What is the role of Tfh?

A

support B cell differentiation?

26
Q

What will CD8+ cells recognise?

A

antigenic peptides bound to MHC I proteins

27
Q

What is a CD8+ cell also known as?

A

a cytotoxic T cell (kills infected cells)

28
Q

How does a cytotoxic T cell cause apoptosis?

A
  1. Cytotoxic T-cell recognises and binds to virally infected cell
  2. T-cell programs the target for death by inducing DNA fragmentation
  3. T-cell binds to its next target
  4. The target cell dies by apoptosis
29
Q

What are the four tasks that the immune system needs to carry out?

A
  • distinguish self from non-self
  • effective removal of pathogens
  • self regulation
  • memory of pathogens encountered in the past