Immunology 4- Acquired immune response and antibodies Flashcards

1
Q

What two signals do B cells need to become fully activated and clonal proliferate?

A
  • The antigen

- ‘helping’ signals

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2
Q

What do activated B cells differentiate into?

A

Plasma cells.

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3
Q

What are plasma cells?

A

Antibody secreting cells which are much larger than B cells and have many RER, meaning they can produce many antibodies.

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4
Q

In what ways can B cells mutate and produce better antibodies?

A

Switch from low to high affinity antibody production.

Switch the class of antibody they produce (e.g. IgM> IgG).

Differentiate into long-lived plasma cells and long-lived memory B cells.

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5
Q

Are IgM antibodies high or low affinity molecules?

A

Low affinity.

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6
Q

Which type of antibody do plasma cells first produce?

A

IgM antibodies.

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7
Q

What are the two signals needed from non-protein antigens for B cell activation?

A

1- BCR + antigen

2- PRR + PAMP

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8
Q

why do B cells not need a second signal for antigens with multiple antigenic epitopes?

A

There is enough interaction to activate the B cell without a secondary signal.

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9
Q

What do non-protein antigens and antigens with repetitive antigenic epitopes lead to?

A
  • low affinity antibodies
  • short lived plasma cells
  • no memory cells
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10
Q

What are the two signals needed from protein antigens for B cell activation?

A

1- BCR binding to antigen

2- Help from Th cells

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11
Q

Through what process do B cells internalise protein antigens?

A

Endocytosis

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12
Q

What do B cells do to receive help from Tfh cells?

A

The peptides derived from chopping up protein antigens are presented on the B cell surface as an MHC-II peptide signal. The Tfh cell can then bind to this signal. Tfh helps by secreting co-stimulatory molecules to help the B cell.

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13
Q

How do Tfh cells help B cells?

A

They release co-stimulatory molecules. (help B cells produce antibodies)

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14
Q

What is the germinal centre reaction?

A

Rapid proliferation

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15
Q

What are the two parts of an antibody?

A
  • The ‘recognition function’ at the top, mediates binding to antigen by variable region sites
  • The ‘effector function’ at bottom, mediates clearance mechanisms by interaction of its heavy chain constant region and the effector molecules (complement or Fc receptors)
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16
Q

Describe IgM.

A
  • In its membrane-bound monomeric form, IgM serves as the B cell antigen receptor (mediates B cell activation)
  • In its secreted (from plasma cells) pentameric form, IgM is the first Ig type produced during a humoral immune response, it is present in plasma and secretory fluids, its involved in agglutination and complement system activation
17
Q

What is agglutination?

A

The action of an antibody when it cross-links multiple antigens producing clumps of antigens.

Agglutination increases the efficacy of pathogen elimination by enhancing phagocytosis. It prevents viruses from binding and infecting host cells

18
Q

What two antibodies mediate agglutination?

A

IgM and IgG.

19
Q

Which pathway in the complement system is activated by the Fc region on IgM and IgG?

A

the classical pathway

20
Q

Describe IgG.

A
  • Most abundant antibody in normal human serum
  • Present in serum in a monomeric form (IgA)

Functions:
• Neutralisation
• Agglutination
• Complement system activation through classical pathway
• Foetal immune protection (transported across the placenta, directly into the foetal blood circulation)
• Opsonisation
•NK cells activation

21
Q

What is neutralisation?

A

A process mediated by specific antigen binding to high affinity IgG and secretory IgA antibodies which is blocking viral entry

22
Q

What does IgE do?

A

Triggers allergic responses, involves mast cells.

23
Q

Describe IgA.

A
  • Second most abundant Ig type
  • Present in serum in a monomeric form
  • Does neutralisation
  • Present in secretory fluids in dimeric form (secretory IgA, sIgA) which is good for neonatal defence (protects GI tract) and neutralisation at mucosal sites
24
Q

Describe IgD.

A

In membrane-bound monomeric form, IgD serves as a B cell antigen receptor (mediates B cell activation)

25
Q

Which antibody is a great opsonin?

A

IgG.

26
Q

How can phagocytes bind to IgG?

A

Phagocytes express an Fc receptor that binds specifically to the constant region of the heavy chain in IgG

27
Q

Which antibody is good at natural killer cell activation?

A

IgG.

28
Q

What do opsonin receptors do?

A

Opsonin receptors trap opsonised antigens in the b cell zone of lymph node. Makes it easier for b cell to bind to it.