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BDS1 > Adaptive immunity 2 (B cells) > Flashcards

Adaptive immunity 2 (B cells) Flashcards

1
Q

Which subset of T cells drive antibody production by B cells?

A

TH2 CD4+ T cells

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2
Q

Where do B cells originate and mature?

A

Bone marrow (from haemopoetic stem cells)

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3
Q

Where are B cells found in large populations?

A

lymph, lymph nodes, spleen, specialised lymphoid tissues (secondary lymphoid organs)

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4
Q

Which branch of the adaptive immune system is driven by B cells?

A

Humoral immunity (produce antibodies)

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5
Q

Function of B cells

A

produce antibodies, and are capable of antigen presentation for T cell activation

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6
Q

What are the 2 main subsets of B cells?

A

plasma cells and memory B cells

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7
Q

How many types of antibodies exist?

A

5

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8
Q

Which professional immune cells are capable of antigen presentation?

A

dendritic cells, macrophages, B cells

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9
Q

How do B cells recognise antigens?

A

via the B cell receptor (BCR) which has extreme diversity

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10
Q

What is the B cell receptor essentially?

A

an antibody (2 of the 5 antibody types are BCRs)

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11
Q

Which of the 2 antibody types form BCRs?

A

IgM or IgD

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12
Q

When does BCR diversity arise?

A

during B cell education in the bone marrow

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13
Q

Where are B cells activated?

A

In the periphery in secondary lymphoid organs (lymph nodes, spleen, specialised lymphoid tissues)

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14
Q

What happens once B cells are activated?

A

differentiate into plasma cells and memory B cells

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15
Q

Function of plasma cells

A

produce antibodies

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16
Q

function of memory B cells

A

produce a faster antibody response during a reinfection

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17
Q

Where does B cell education occur?

A

In the bone marrow

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18
Q

What happens during B cell education?

A

VDJ recombination and negative selection

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19
Q

What process creates diversity in the BCR?

A

VDJ recombination

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20
Q

Which region of the BCR is affected by VDJ recombination?

A

variable region (antigen binding site) - constant region remains the same.

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21
Q

Why do B cells not need to undergo positive selection?

A

B cells do not need to interact with MHC receptors on host cells (unlike T cells)

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22
Q

Which gene segments code for the light chain of BCRs?

A

V (variable) and J (joining)

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23
Q

Which gene segments code for the heavy chain of BCRs?

A

V (variable), D (diversity), J (joining) - all 3

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24
Q

How is the variable region of BCRs unique?

A

VDJ recombination means that multiple options can be selected for each gene segment leading to a huge number of possible gene combinations.

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25
Q

Function of B cell negative selection

A

ensures there are no self reacting B cells circulating that will recognise and target self antigens

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26
Q

Where does negative selection occur?

A

bone marrow

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27
Q

How does negative selection occur?

A

specialised bone marrow cells present self antigens to B cells which are expressing antibodies/BCR (IgM, IgD)

28
Q

What happens if B cells do not bind to self antigens during negative selection?

A

B cells are released from the bone marrow and migrate to secondary lymphoid tissues

29
Q

What happens if BCR binds to the self antigen during negative selection?

A

the self-reacting B cell is engulfed and removed by macrophages

30
Q

How can autoimmune disease arise?

A

if there is a breakdown in negative selection (and self-reactive B cells are released)

31
Q

What are B cells called when they leave the bone marrow?

A

naive B cells (not yet encountered antigens)

32
Q

Examples of specialised lymphoid tissues

A

(found in barrier and mucosal sites) tonsils, adenoids, Peyer’s patches

33
Q

What are the 2 types of B cell activation?

A

Thymus-dependent (requires help of T cells) and thymus-independent (without help from T cells)

34
Q

Which T cells enable thymus-dependent activation of B cells?

A

CD4+ TH2 cells and TFH (T follicular helper cells)

35
Q

How can B cells be activated without T cell involvement?

A

Thymus-independent activation - involves the BCR recognising an antigen, and the PRRs (e.g. TLR) on the B cell recognising a PAMP (component of microorganism e.g. LPS) at the same time

36
Q

What happens when naive B cells are activated?

A

They differentiate into plasma cells which initially releases IgM. Naive B cells also differentiate into memory B cells but only in thymus-dependent activation.

37
Q

How are B cells activated by thymus-dependent activation?

A
  1. B cells present antigen to T cells (CD4+ TH2 and TFH cells)
  2. Costimulatory molecules of B cell (CD40) and T cell (CD40L) interact
  3. T cell releases cytokines which leads to B cell differentiation
38
Q

Which cells do B cells differentiate into during thymus-dependent activation?

A

plasma cells and memory B cells

39
Q

What cells do B cell differentiate into during thymus-independent activation?

A

plasma cells only

40
Q

Which type of B cell activation does not provide long-term immunity?

A

thymus-independent B cell activation because memory B cells are not produced

41
Q

What does B cells activation lead to?

A

class switching

42
Q

What is the first type of antibody produced by plasma cells following B cell activation?

A

IgM

43
Q

What is class switching?

A

When B cells change the production of antibodies from one type to another (IgM -> IgG)

44
Q

Why does class switching occur?

A

to produce a more effective immune response (IgM has a weak response, other antibodies have different functions too)

45
Q

How does class switching occur?

A

by gene rearrangement to alter the constant region which allows the production of antibodies with different structures but with the same antigen binding site

46
Q

What features determine the effectiveness of antibodies?

A

affinity and avidity

47
Q

What is the affinity of an antibody?

A

strength of binding to antigen

48
Q

What is the avidity of an antibody?

A

the number of binding sites the antibody has

49
Q

Which antibodies have low avidity?

A

IgD, IgM, IgE, IgG (only 2 antigen binding sites)

50
Q

Which antibodies have high avidity?

A

IgA (4 antigen binding sites) and secreted IgM (10 binding sites)

51
Q

What is the structure of secreted IgM?

A

pentametric complex - made of 5 antibodies so a total of 10 antigen binding sites

52
Q

Which antibodies have low affinity?

A

IgM, IgD, IgA

53
Q

Which antibodies have high affinity?

A

IgG and IgE (therefore are most effective and so are produced the most)

54
Q

What are the 5 types of antibodies / immunoglobulins?

A

IgM and IgD (BCRs), IgG, IgE, IgA

55
Q

Example of where secretory IgA is found

A

saliva

56
Q

What are the functions of B cell antibodies?

A

Neutralisation, opsonisation (tag microorganisms/allergens for removal), activate the complement cascade

57
Q

Which antibody has the function of neutralisation?

A

secretory IgA - binds to 4 antigens simultaneously and prevents microorganisms attaching to host cells.

58
Q

Function of opsonisation

A

antibodies (opsonins) tag microorganisms and allergens for removal which initiates phagocytosis (e.g. by macrophages) or degranulation (of NK, mast cells, eosinophils, basophils)

59
Q

Which pathway of the complement cascade can be activated by antibodies?

A

classical pathway

60
Q

What does the complement cascade produce?

A

Anaphylatoxins

61
Q

Functions of anaphylatoxins

A

recruit immune cells to the site of infection, form membrane attack complexes, drive opsonisation for phagocytosis

62
Q

Which cells play a role in vaccinations?

A

B and T cells (adaptive immune system)

63
Q

Which antibodies are produced in a primary response (e.g. vaccination)?

A

initially IgM which is then switched to IgG

64
Q

Which antibodies are produced in a secondary response?

A

Mainly IgG (and some IgM)

65
Q

Why is a much larger concentration of IgG released more rapidly in a secondary response?

A

memory B cells are primed to produce IgG upon re-exposure to a specific antigen

BDS1 (71 decks)

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