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1d. Microbiology, Pathology, Infection & Immunity > L95: Adaptive Immunity II > Flashcards

L95: Adaptive Immunity II Flashcards

1
Q

What are the two major cells of lymphoid organs?

A
  • T-cells;

- B-cells.

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2
Q

Where do B-cells mature?

A

Bone marrow

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3
Q

Where are B-cells found?

A
  • Circulation (blood and lymph);

- Lymphoid organs.

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4
Q

On what surface are antigens recognised by B-cells?

A

B-cell receptors (BCR)

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5
Q

What, effectively, is a BCR?

A

Antibody

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6
Q

What are plasma cells?

A

Activated B-cells

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7
Q

What do plasma cells produce?

A

Antibodies

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8
Q

What molecules recognise antigens?

A
  • T-cell receptors (TCR);
  • B-cell receptors (Immunoglobins [Ig]);
  • Major histocompatibility complexes (MHC proteins).
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9
Q

What enables variation of antigen reception?

A

Multiple genes encoding for antigen receptors (TCR, Ig, MHC)

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10
Q

What is the general structure of an antibody (immunoglobin- Ig)?

A
  • Y-shaped;
  • Heavy chain and light chain duplex;
  • Fab (antigen-binding) region: variable;
  • Fc (constant) region: constant.
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11
Q

What are the different classes of antibodies?

A

5 classes:

  • IgA;
  • IgD;
  • IgE;
  • IgG (1-4);
  • IgM.
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12
Q

What are IgAs and what do they target?

A
  • Immunoglobulin A;
  • Found in secretions such as tears, saliva, mucus;
  • Attack pathogens before they gain entry to internal tissues.
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13
Q

What are IgDs and what do they target?

A
  • Immunoglobulin D;
  • Found on the surface of B-cells (BCR);
  • Can bind to antigens in ECM.
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14
Q

What are IgEs and what do they target?

A
  • Immunoglobulin E;
  • Attack individual molecules found on the surface of basophils and macrophages (e.g. pollen);
  • Allergen response;
  • Stimulate histamine release.
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15
Q

What are IgGs and what do they target?

A
  • Immunoglobulin G;
  • 80% of immunoglobulins;
  • Attack pathogens (bacteria, viruses etc.).
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16
Q

What are IgMs and what do they target?

A
  • Immunoglobulin M;
  • BCR;
  • Macroglobulin (large in size);
  • Function early on in the immune response;
  • IgM to IgG response.
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17
Q

What is the IgM to IgG response?

A
  • IgMs released after first encounter with antigen;

- IgM production declines as IgG production accelerates.

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18
Q

What are the three effector functions of antibodies?

A
  • Neutralisation;
  • Opsonisation;
  • Complement activation.

(all to prevent bacterial or viral adhesion)

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19
Q

What is opsonisation?

A

Antibodies sticking to the surface of pathogens to promote phagocytosis by phagocytes or destruction

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20
Q

Where are the B-cells produced?

A

Bone marrow

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21
Q

Where are the B-cells specialised?

A

Bone marrow

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22
Q

What happens at each development stage of B-cells?

A

Rearrangement of immunoglobulin heavy and light chains

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23
Q

Where do B-cells migrate to?

A

Lymphoid organs

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24
Q

What is a BCR?

A

Antibody

25
Q

What do heavy chains comprise of?

A
  • V, variable;
  • D, diversity;
  • J, joining genes.
26
Q

What do light chains comprise of?

A
  • V, variable;

- J, joining genes.

27
Q

What are the main types of immature B-cells?

A

IgM

28
Q

What are the main types of mature B-cells?

A

IgG (still naive)

29
Q

What is negative selection?

A

Selection of B-cells to ensure there is no self-antigen reaction. If reaction, not selected, apoptosis.

30
Q

How are B-cells activated?

A
  • Thymus-dependent (TD), T-cell help OR;

- Thymus-independent (TI).

31
Q

Where does B-cell activation mainly happen?

A

Lymphoid organs

32
Q

What is the type of B-cell activation dependent on?

A

Antigen

33
Q

What does B-cell activation lead to?

A

A rise in the number of plasma cells (antibody factories)

34
Q

What are the stages of TD B-cell activation?

A
  • Interaction between T-cell and BCR with CD40 and CD40L co-receptor binding;
  • Cytokines released from Th cells induce proliferation;
  • Generation of plasma cells, which produce antibodies;
  • Production of memory cells;
  • Plasma cells initially produce IgM, before class switching to IgG.
35
Q

By what process does class-switching happen?

A

Gene rearrangement

36
Q

What is affinity maturation?

A

The increased binding strength of an antibody to an antigen after repeated exposure

37
Q

What is avidity?

A

The ability of antibodies to form complexes (antibody-antibody binding)

38
Q

How does the affinity of an antibody to an antigen effect the immune response?

A

Greater affinity = greater response

39
Q

Which B-cell response (TI or TD) leads to an immunological memory?

A

TD

40
Q

What are the stages of TI B-cell activation?

A
  • Direct binding of antigen (LPS) to BCR;

- B-cells differentiate into plasma cells and produce IgM.

41
Q

Which B-cell response (TI or TD) is stronger?

A

TD

42
Q

Explain the basis of vaccination.

A
  • Based on an immunological response developed in the primary response to exposure to an antigen;
  • Primary response is slow, IgM acts early but these cells undergo class-switching to IgG;
  • Primary response leads to the generation of memory T and B-cells;
  • Upon second exposure there is a pool of cells waiting to respond immediately;
  • Cells are also primed (IgG rather than IgM) so the response is stronger.
43
Q

How does a secondary response differ to a primary and what influences this?

A
  • Stronger and quicker response;
  • Stronger because cells are primed (IgG rather than IgM);
  • Quicker as a pool of cells are ready to respond immediately.
44
Q

What other molecules are required for cross talk?

A

Co-receptors CD40 and CD40L

45
Q

What is immunologic tolerance?

A

A state of immune unresponsiveness to certain antigens (self/ commensals etc.)

46
Q

What type of response is immunologic tolerance?

A

Active and specific

47
Q

What type of immune cells (adaptive) are tolerised?

A

Both, B and T-cells but it is more important to tolerise T-cells

48
Q

Why is it more important to tolerise T-cells?

A

Most B-cells can’t make antibodies without T-cells so immune response would most likely be stopped before self-reaction

49
Q

What are the two types of tolerance?

A

Central and peripheral

50
Q

Where does central T-cell tolerance happen?

A

Thymus (positive and negative selection)

51
Q

Where does peripheral T-cell tolerance happen?

A

Out with the thymus and bone marrow, i.e. tissues and lymphoid organs (T-cell activation)

52
Q

Explain peripheral T-cell tolerance?

A
  • 3 signal process;
  • Both signals 1 and 2 must happen before signal 3;
  • If signal 1 but no 2, anergy;
  • If signal 1 and 2 but no 3, apoptosis;
  • Tregs also block self-binding.
53
Q

Where does central B-cell tolerance happen?

A

Bone marrow (negative selection ONLY)

54
Q

Where does peripheral B-cell tolerance happen?

A

Secondary lymphoid organs

55
Q

Why is a B-cell self-reaction less likely to happen than a T-cell self-reaction?

A

Self-reactive B-cells still require help from self-reactive T-cells (independently tolerated)

56
Q

When does central tolerance happen?

A

During the development of B and T-cells

57
Q

How are autoimmune diseases initiated?

A

Branch of tolerance

58
Q

Give three examples of autoimmune diseases.

A
  • Psoriasis;
  • Rheumatoid arthritis;
  • Graves’ disease (thyroid);
  • Hashimoto’s thyroiditis;
  • Lupus;
  • Sjogren’s syndrome;
  • Chron’s disease;
  • Multiple sclerosis;
  • Type-1 diabetes.

1d. Microbiology, Pathology, Infection & Immunity (2 decks)

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