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POM > lymphocytes > Flashcards

lymphocytes Flashcards

1
Q
  • What type of immunity are T cells a part of?
  • What type of immunity are B cells a part of?
  • What is specificity of B and T cells due to?
A

Cell mediated

Humoral

respective BCRs and TCRs

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2
Q
  • Define epitope
  • What structure of epitopes do T cells recognise?
  • What structure of epitopes do B cells recognise?
A

Region of an antigen which the receptor binds to

Linear epitopes in the context of an MHC molecule - Primary structure

Structural epitopes - the 3D structure of the antigen in space
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3
Q
  • Explain the process of clonal expansion
A

Each lymphocyte bears a single, unique receptor

Interaction between a specific foreign molecule and that receptor leads to activation and clonal expansion (multiple copies of same cell)

Differentiated effector cells of that lineage will bear the same receptor
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4
Q
  • Explain the antigen receptor diversity problem

- How is antigen receptor diversity generated?

A

We need to encode a large Repertoire of lymphocyte receptors

We need 10^15 different genes for each different antibody, but we only have 25000 genes total for all functions

Each BCR chain is encoded by separate multi-gene families on different chromosomes.
During B cell maturation these gene segments are brought together.
This process is called Immunoglobulin gene rearrangement

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5
Q

what are the three types of chain that form BCR?

  • What is the role of an MHC?
A

kappa, lambda, gamma

To bind peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T cells

Critical in surgery and donor matching

defines self and non self

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6
Q
  • Describe the structure of MHCI and where are they found?

- Describe the structure of MHCII and where are these found?

A

Single variable alpha chain plus a common beta- microglobulin
On all nucleated cells

2 chains - alpha and beta 
Normally only on "professional" antigen presenting cells
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7
Q
  • What gene in humans encodes for MHC?

- How are MHC genes expressed?

A

HLA genes

MHC is polygenic - 3 class I and 3 class II loci 
Co-dominant (maternal and paternal both expressed)
Each person can have up to 6 of the variations of the gene if completely heterozygous
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8
Q
  • What are the 2 T cell families?
  • Which MHC is presented to CD8 T cells?
  • Which MHC is presented to CD4 T cells?
A

CD4(helper) and CD8(killer)

MHC1

MHC 2

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9
Q

Where are intracellular MHC/TCR interactions processed?

what are they presented on

what are they presented to

which domain of MHC molecule does CD8 cell bind to

A

Cytosol

MHC1

CD8 T cells

alpha 3 domain

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10
Q

Where are extracellular MHC/TCR interactions processed?

what are they presented to

what is it presented on

which domain on MHC?

A

endosomes

CD4 T cells

MHC2

beta 2

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11
Q
  • Explain what CD4 T helper cells do
A

They produce cytokines (family of inflammatory mediators)

Influence the outcome of the immune response.
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12
Q
  • List all 5 CD4 T helper cell classes
A

Th1 - boosts cellular immune response

Th2 - boosts multi-cellular response

Th 17 - controls bacterial and fungal infection

Treg (Th0) - limits immune response

Tfh - pro-antibody
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13
Q
  • Which CD4 T helper cell class are pro-inflammatory?
  • Which CD4 T helper cell class includes interleukins 4,5 and 13?
  • What CD4 T helper cell class is pro-allergic?
  • Which class of CD4 T cells includes interleukins 6, 17 & 23?
A

Th1 and Th17

Th2

Th2

Th17

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14
Q

what cytokines are released by a:

  • TH1 response
  • Tfh response
  • Treg response
A

IL-12
TNF- tumour necrosis factor
INF- Gamma

IL-21

IL-10, TGF-beta

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15
Q
  • How do cytotoxic T cells (CTL) kill their target cells?

- How is apoptosis characterised?

A

Apoptosis

Fragmentation of nuclear DNA
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16
Q
  • What do Cytotoxic T Cells store and then release after target recognition?
  • How is apoptosis carried out by CD8 T-cells?
A

Perforin, granzymes, granulysin (all in cytotoxic granules)

CD8 T cell makes Perforin hole in the infected cell
Injects granzymes into the cell
Granzyme triggers cascade of events within target cell which leads to cell death and kills anything within inside of target cell
17
Q
  • Outline the process of how CD8 cells kill cells once they are infected
A
  1. Virus infects the cell and releases its contents
    1. Cell now starts making viral proteins
    2. Displays these as non-self MHC
    3. CD8 cell detect non-self MHC and attacks
    4. CD8 cell kills the virally infected cell
18
Q
  • What is the main purpose of B cells?

- What are the 3 core protective roles of B cells?

A

To make antibodies

- Neutralisation - antibody prevents bacterial adherence to host cell
- Opsonisation - promotes phagocytosis
- Complement Activation - enhances opsonisation and lyses some bacteria
19
Q
  • List all of the antibody classes
A
  • IgG: highest opsonisation and neutralisation activities
    classified into four sub classes (IgG1, IgG2, IgG3, IgG4)
    • IgM: Pentamer, produced first upon antigen invasion, increases transiently
    • IgA: form dimers after secretion
      expressed in mucosal tissues
    • IgD: unknown function
    • IgE: Involved in allergy
20
Q
  • Which antibody class is involved in type I hypersensitivity?
  • Which antibody class is expressed in mucosal tissues?
  • Which antibody class has highest opsonisation activity?
  • Which antibody class has highest neutralisation activity?
A

IgE

IgA 

IgG

IgG
21
Q
  • Where does B cell generation and maturation occur?

- What do mature B cells migrate into from the bone marrow?

A

In bone marrow in the absence of antigen

Circulation and lymphoid tissues
22
Q
  • What do naïve B cells require to be activated?

- Describe the Thymus Independent activation of B cells

A

Accessory signal:

1. Directly from microbial constituents (thymus independant)
2. From a T helper cell

Thymus independent antigens directly activate B cells without help of T cells- usually polysaccharide
Second signal required is provided by a microbial PAMP eg LPS from gram negative bacteria

23
Q
  • Outline the process by which B cells are activated by T cells (Thymus Dependent antigens)
A
  1. Membrane bound BCR recognises antigen
    1. Receptor-bound antigen is internalised and degraded into peptides
    2. Peptides associate with “self” molecules (MHC class II) and is expressed at the cell surface
    3. This complex is recognised by matched CD4 T helper cell that was activated by dendritic antigen presenting cell
    4. B cell activated

POM (47 decks)

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