T and B cells, cytokines and dendritic cells Flashcards

1
Q

How do cells of the immune system communicate between themselves, and with other non-immune cells?

A
  1. Cell-cell contact (signalling through receptor -ligand interactions between membranes of different cells, (eg MHC and TcR)
  2. Secretion of soluble factors that initiate responses and signals by binding to specific receptors (e.g. cytokines)
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2
Q

Define cytokines.

A

Small polypeptides, around 25,000 Mr released by cells in response to an activating stimulus. Can have autocrine, paracrine and endocrine (latter limited by ability to enter circulation and half-life) actions.

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3
Q

Define chemokines.

A

A class of cytokine that has chemoattractant properties, ie induces cells to migrate towards the source.

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4
Q

Define interleukins.

A

Cytokines secreted by leucocytes

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5
Q

Identify the main groups if chemokines. Why were these groups get named the way they did ?

A
  1. CC (which bind to receptors CCR1 to 9)
  2. CXC (which bind to CXCR1 to 5)

Named due to spacing of cysteine residues close to amino terminus (two N-terminal cysteines of CXC chemokines separated by one amino acid VS two adjacent cysteines near their amino terminus).

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6
Q

Describe the main features of IL-8, including source, receptors, target cells, major effects, and type of cytokine.

A
  • CXC Chemokine
  • Source: Monocytes, macrophages, fibroblasts, keratinocytes, endothelial cells
  • Receptors: CXCR1 and CXCR2
  • Target cells: Neutrophils and naive T cells
  • Major effects: Mobilises, activates and degranulates neutrophils + Angiogenesis + induces chemotaxis in target cells, causing them to migrate toward the site of infection and induces phagocytosis once they have arrived
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7
Q

Describe the function of Interleukin 2. How is it secreted ?

A

Activates and grows T cells (growth factor for other T cells)
Secreted by T cells

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8
Q

Describe the function of Interleukin 4.

A

Activates and grows B cells + switches them to produce IgE (important in allergy)

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9
Q

Describe the function of Interferon gamma.

A

Activates strong cell mediated responses (e.g. Cytotoxic T lymphocytes) + Causes upregulation of MHC class 1 and 2.

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10
Q

Describe the function of TNF-alpha. How is it secreted ?

A

Pro-inflammatory (activates vascular endothelium and increases vascular permeability)
Secreted by T cells

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11
Q

What treatment is there to dampen down pro-inflammatory response of TNF (e.g. in rhumatoid arthritis) ?

A

Inflixamab

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12
Q

Do cells produce one type of cytokine only or more than one ?

A

A cell will tend to produce different cytokines with different effects on cells

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13
Q

How do neutrophils access infection sites ?

A

Neutrophils access infection sites by diapedesis

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14
Q

What is a problem associated with TNF alpha release ?

A

Its release normally triggers local protection (by allowing lymphocytes to travel thanks to decreased vascular permability, but can induce systemic shock –> if overproduction of TNF-alpha)
Notably including systemic oedema, decreased blood volume, hypoproteinemia, neutropenia followed by neutrophillia, collapse of vessels. May result in death

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15
Q

Describe the process through which Interleukin 2 induces proliferation of T cells.

A
  1. Naive T cells express the low affinity IL-2 receptor
  2. Activated T-cells express the high affinity IL-2 receptor and secrete IL-2
  3. Binding of IL-2 to high affinity receptor sends a signal to the T cell
  4. The signal sent from IL-2 receptor induces T cell proliferation
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16
Q

Identify the types of CD4 T cells, distinguishing between the two.

A

TH1 CELL (cell mediated immunity):

  • Produce cytokines which result in:
  • Macrophage activation
  • B cell activation
  • Production of opsonising antibodies

TH2 CELL (antibody responses:

  • Produce cytokines which result in:
  • General activation of B cells to make antibodies
17
Q

Describe the activation of B cells by TH2 cells.

A
  1. Antigen recognition induces expression of CD40 ligand and cytokines by the TH2 cell, which activates the B cell
  2. B cell proliferation and differentiation to antibody-secreting plasma cells.
18
Q

Define dendritic cells and decribe their function.

A
  • Professional antigen presenting cells that sit at the interface between the innate and adaptive immune response.
  • Highly phagocytic, sampling their external environment. Upon stimulation, cease phagocytosis and migrate to lymph nodes.
  • In lymph nodes (clusters of B cells and T cells around the dendritic cells), activate T cells and influence B cells, to initiate immune response
19
Q

Where are dendritic cells found ?

A

In most surface epithelia

20
Q

Provide some of the other names of dendritic cells.

A

Langerhans cells in skin, interdigitating cells, follicular dendritic cells (FDC), veiled cells (when travelling in circulation)

21
Q

How long do follicular dendritic cells hold onto antigens for ?

A
  • FDC can hold on to antigen for extended periods of time, possibly many days (good at immunological memory)
  • The antigen is in the form of antigen-antibody-complement complexes, bound to Fc and complement receptors on the FDC surface
  • The complexes do not appear to undergo internalisation
22
Q

True or False: Plasma cells are activated B lymphocytes

A

True

23
Q

How do dendritic cells link to innate immunity ?

A
  • Express Pattern Recognition Receptors (PRR, recognise patterns that are in pathogens and not in our cells ), members of the Toll-like receptor Family (TLR)
  • Several PMN (polymorphonuclear leukocytes) cells also express PRR
24
Q

Where in/on the dendritic cells are Toll-like receptors located ?

A

These sit on dendritic cell surface.

25
Q

List the ligand of the first 11 Toll-Like Receptors on Dendritic Cells.

A
  • TLR1 and 2: lipopeptides
  • TLR3: dsRNA
  • TLR4: Lipopolysaccharide, heat shock proteins
  • TLR5: flagellin
  • TLR6: lipoproteins
  • TLR7: ?
  • TLR8: ssRNA
  • TLR9: CpG(cytosine-phosphate-guanosine, bacterial DNA
  • TLR10: ?
  • TLR11: bacterial components.