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Principles 2018 > Immunology Part 5 > Flashcards

Immunology Part 5 Flashcards

1
Q

What do activated B cells do?

A
  • Produce short-lived plasma cells
  • Low affinity, antigen-specific antibodies are secreted

Activated B cells can also produce memory B cells, these product high affinity antigen specific antibodies

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2
Q

Describe the recognition function of antibodies

A

The variable regions allow binding to antigen

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3
Q

Describe the effector function of antibodies

A

Clearance mechanisms mediated interaction of the constant region with effector molecules

  • complement
  • Fc receptors
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4
Q

What is the role of IgM?

A

Serves as the B cell antigen receptor
-activates b cells

First Ig produced in immune response
(mmmmneong)

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5
Q

What is the function of IgM?

A

Pentamier in plasma and secretory fluids;

  • agglutination (immune complex formation)
  • complement system activation
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6
Q

What is agglutination?

A

When an antibody cross-links multiple antigens forming a clump of antigens

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7
Q

What is agglutination mediated by?

A

Specific antigen binding to IgM and IgG antibodies

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8
Q

What does agglutination do?

A

Increases the efficacy of microbial elimination by phagocytosis

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9
Q

What initiates complement system in the classical pathway?

A

Specific antigen binding to IgG and IgM antibodies

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10
Q

What happens when a specific antigen binds to IgG and IgM antibodies?

A

Induces a conformational change in the constant regions of IgM and IgG heavy chains which exposes multiple binding sites for C1, the first component of the Classical Activation pathway of the Complement System

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11
Q

Describe the structure and abundance of IgG?

A

most abundant in human serum (normally)

dominant Ig type produced during a secondary memory response

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12
Q

What are the functions of IgG?

A 
Agglutination 
Complement system activation
Foetal immune protection 
Neutralisation
Opsonisation
Natural Killer cell activation
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13
Q

Which antibodies are transported across the placenta into foetal blood?

A

IgG

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14
Q

What is neutralisation?

A
  • Prevents pathogens from infecting host cells

- Prevent toxins from disrupting normal cell function

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15
Q

What triggers neutralisation?

A

Binding of high affinity neutralising antibodies to antigens is protective
IgG
Also dimeric IgA (in secretions)

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16
Q

What is opsonisation?

A

Enhanced phagocytosis of encapsulated bacteria

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17
Q

What initiates opsonisation?

A

Specific antigen binding

18
Q

What mediates opsonisation?

A

Special Fc receptors that bind specifically to the constant region of the Iggamma chain of IgG

19
Q

Describe natural killer cell activation in antibody-dependant cell mediated cytotoxicity?

A

NK cells Fcgamma receptor binding to IgG on infected cell can trigger apoptosis of infected cell

20
Q

What is the function of IgD?

A

In membrane-bound form serves as b cell antigen receptor (monomer)
Functions to activate B cells

21
Q

What is the second must abundant serum Ig?

A

IgA

22
Q

What is the monomeric form of IgA?

A

Present in serum

functions to activate B cells

23
Q

What is the dimeric form of IgA

A

Present in secretory fluids
functions;
-neonatal defence
-neutralisation at mucosal sites

24
Q

What is the role of IgE?

A

Trigger allergic response

25
Q

How are antibodies of the same specificity but different Ig class produced?

A

During B cell activation, B cells can switch the Ig heavy chain constant region gene segment that they use

Retain the original Ig heavy and light chain gene hypervariable gene segments

Process is induced by the specific cytokines

26
Q

Describe the effector functions of activated CD4+T cells?

A

Produce helper t cells which produce

  • TH1
  • TH2
  • Tfh
  • Th17
  • TREG
27
Q

What is the role of Th1 Cells?

A

Killing of intracellular bacteria

28
Q

What is the role of Th2 cells?

A

Killing of helminths

29
Q

What is the role of Tfh cells?

A

B cell co-activation

30
Q

What is the roll of Th17 cells?

A

Killing of extracellular pathogens

31
Q

What is the roll of regulatory T cells?

A

Lymphocyte suppression

32
Q

What do effector Th cells do?

A

Stimulate other immune cells

  • CD4+T
  • CD8+
  • macrophage
  • B cell
33
Q

How do effector Th cells help T cell responses?

A

They secrete interleukin 2 which stimulates proliferation and differentiation of antigen-activated T cells (and antigen-activated B cells)

34
Q

How do effector Th1 cells help macrophages?

A

Effector TH1 cells migrate from secondary lymphoid tissues into infected tissue sites.

TH1 cells are re-activated by tissue-resident macrophages in an antigen-specific manner

TH1 cells express co-stimulatory molecules (e.g. IFNg) that hyper-activate macrophages, enhancing their killing activities and pro-inflammatory cytokine production.

35
Q

How do tFH cells help B cells?

A

help B cells respond effectively to protein antigens (they provide Signal 2)

  • protein antigen bound to BCR is internalised
  • antigen is degraded and peptides are presented on the B cell surface in complex with MHC-II
  • effector Tfh move into B cell zone of lymph node, they are re-stimulated by B cells in an antigen-specific manner and start to express co-stimulatory molecules
  • re-activated effector Tfh cells stimulate the B cell to clonally proliferate
  • the re-activated effector Tfh cells secrete cytokines that activate the B cell and stimulate the germinal centre response
36
Q

What is the germinal centre response?

A 
B cell proliferation
Differentiation into Plasma cells 
Differentiation into Memory B cells
Ig heavy chain class switching
Generation of high affinity antibodies
37
Q

Describe the pathway of CD8+ cells effector function?

A

Produce cytotoxic T lymphocytes and kill infected host cells

38
Q

What do CTLS do?

A

CTLS exit lymph nodes, migrate to sited of infection, recognise and kill infected tissue cells in an antigen specific manner

39
Q

Describe the process of CTL killing?

A
  1. CTL recognises and binds to virally infected cell via MHC i
  2. CTL programs target for death, inducing DNA fragmentation
  3. CTL migrates to new target
  4. target cell dies by apoptosis
40
Q

How do CTLs and NK cells kill infected host cells?

A

Release perforin and granzyme molecules from granules

Perforin: polymerises to form pore in target membrane

Granzymes: serine proteases which activate apoptosis once in the cytoplasm of target cell

Granulysin: induces apotosis

41
Q

What is Fas ligand mediated killing?

A

Externally driven apoptotic signals which initiate caspase cascade and apoptosis

Principles 2018 (34 decks)

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