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IAI > Antibody, Lymphocytes & Generation of Diversity (#2) > Flashcards

Antibody, Lymphocytes & Generation of Diversity (#2) Flashcards

1
Q

List the general functions of antibodies

A
  • neutralise toxins + viruses
  • opsonise pathogens
  • activate complement cascade to kill pathogens
  • agglutinates particles
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2
Q

How do antibodies neutralise toxins + viruses?

A
  • binds to them + blocks interactions with other cells

- as it stops toxins/virus binding to its receptor to prevent entry into target cell

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3
Q

How do antibodies opsonise pathogens?

A
  • binds to them to promote phagocytosis + killing activity by other cells by recognition of Fc receptors on macrophages
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4
Q

How do antibodies agglutinate pathogen debris, viruses etc?

A
  • antibody has more than 1 binding site so can cross-link antigens together + disarm them by making them into complex
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5
Q

What is important about IgG in serum?

A
  • main serum antibody

- gen measurement of antibody titre in serum in response to vaccine

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6
Q

What is IgG good at?

A
  • opsonisation (coating pathogens so phagocytic cells can recognise them)
  • many cells have Fc receptors for IgG
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7
Q

What happens to pathogens coated in IgG?

A
  • targets for killing by NK cells = antibody-dep cellular cytotoxicity - also depends on Fc receptors
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8
Q

List the subclasses of IgG and how are they named?

A
  • IgG1, IgG2, IgG3, IgG4

- most (IgG1) to least abdundant (IgG4) in serum

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9
Q

How is IgA found in serum?

A

as a monomer

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10
Q

How is an IgA dimer formed?

A

2 monomers joined by joining J chain

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11
Q

Describe how dimeric IgA is used in the gut lumen?

A

1) plasma cells secrete IgA
2) IgA binds to receptor (secretory component)
3) IgA then transported into gut lumen
4) IgA can bind + agglut intestinal bacteria + regulate pops

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12
Q

What is dimeric IgA good at + why?

A
  • agglut + neutralising bacteria bc it has 4 binding sites
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13
Q

How does IgA retain antigen to mucus?

A
  • charge CHO rich SC of secreted IgA can bind to mucus

- can retain antigens on mucus surface to prevent them from causing damage

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14
Q

What is special about IgM?

A
  • 1st antibody made in immune responses + so 1st one prod in vaccination
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15
Q

Why is the structure of IgM important?

A
  • pentamer so has 10 poss binding sites
  • has high avidity (ability of whole mol to bind rather than 1 particular binding site)
  • agglut v. effective as it can form lattice + also good fixer of complement
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16
Q

What receptors do mast cells have and the consequence of this?

A
  • Fc receptors for IgE

- can bind in absence of allergen

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17
Q

What is conc of IgE in indiv with allergies?

A

higher conc in serum

18
Q

What happens when you breathe in pollen?

A
  • pollen binds + can cross-link IgE on surface of mast cell

- causes mast cell degranulation

19
Q

What causes the symptoms of pollen allergy?

A
  • granules released by mast cells
20
Q

Which antibodies are expressed on surface of newly formed B cells?

A
  • IgM + IgD with same specificity
21
Q

How much IgD is found in serum?

A

v. little

22
Q

Which cells can improve their specificity for antigen + how?

A

only B cells by affinity maturation

23
Q

Why do lymphocytes constantly recirc through blood + lymphoid tissues?

A

inc probab of encountering antigen they can bind to

24
Q

What do secondary lymphoid tissues contain?

A
  • zones of div B cells = germinal centres
25
Q

What are germinal centres?

A

contain highly proliferative B cells that have been inactivated by antigen

26
Q

How can B cells enter germinal centres?

A
  • if encounter specific antigen + have help from T cells
27
Q

What gene encodes the antibody heavy chain?

A

Antibody heavy chain gene

28
Q

How do B cells enter lymphoid

A

through HEV

29
Q

What is somatic hypermutation?

A

as B cells start to div v. rapidly in germ centres, start to mutate variable region genes which are then transcribed + translated

30
Q

What effect does mutation of variable region genes have?

A
  • seq codes for antibody slightly diff to originally bound antigen that supported activation of cell
31
Q

How are new antibody variants selected in the germ centre?

A
  • B cells tested to see which variant of antibody binds to antigen with high affinity
  • those ones survive + prolif further so large pool of antigen reactive cells that bind antigen better than original antibody + stored in depot in germ centres
32
Q

What is affinity maturation?

A

Somatic hypermutation then selection

33
Q

What is class switch of B cells?

A
  • express isotypes other than IgM + IgD
  • antibodies switch from use of 1 constant region to another in germ centre
  • B cell keeps same variable region but ass with constant regions of IgA + IgG
34
Q

Which 2 pops of cells leave germinal centre?

A
  • quiescent circ B memory cells

- plasma cells

35
Q

What are characteristics of quiescent circ B memory cells?

A
  • affinity matured - mutations in antibody genes reflecting this
  • poss class switched - may express IgA/IgG on surface
36
Q

What is function of B memory cells?

A
  • circ to inc probab of encountering same antigen again
37
Q

Where do plasma cells locate to and what do they make?

A
  • bone marrow (most make IgG)

- intestine (most make IgA)

38
Q

How long do plasma cells survive for and their function?

A
  • long lived

- can secrete protective antibodies for a lifetime

39
Q

Describe what happens in the primary immune response

A
  • immunised
  • lag period
  • inc total antibody + IgM in serum
  • total antibody reaches plateau
  • IgM declines + IgG inc
  • IgG + total antibody declines
40
Q

How long is the lag period and what occurs during this time?

A
  • 5 days
  • B + T cells interacting
  • germ centre formation starting
41
Q

What happens after the lag period in the primary immune response?

A
  • total antibody inc as plasma cells gen
  • B cells div in germinal centre
  • IgM is 1st antibody prod
42
Q

What happens at 15 days of primary immune response?

A
  • total antibod plateaus + eventually declines as its a short-lived response
  • IgM declines due to class switch to IgG which inc but eventually declines

IAI (8 decks)

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