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Cellular basis of immunity extra > Extra > Flashcards

Extra Flashcards

1
Q

In which system of the body does dendritic cell activation of B cells occur?

A

In the lymphatic system (you can be more specific than this e.g. within the germinal centres)

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2
Q

The antigen binding receptor on the surface of a B cell is comprised of what?

A

Antibody

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3
Q

Which sub-set of helper T cells has a cytokine profile that stimulates B cell antibody production?

A

TH2

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4
Q

The antigen presented to the B cell by the dendritic cell is comprised of a fungal cell wall glycoprotein. Name a PRR (other than a TLR) found on the surface of dendritic cells which is capable of binding to fungal cell wall carbohydrates

A
  • Dectin-1
  • Dectin-2
  • Mincle
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5
Q

B cells are derived from which lineage of the hematopoietic stem cell?

A

Lymphoid

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6
Q

A mature B cell that hasn’t yet encountered antigen is referred to as what?

A

Naïve

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7
Q

Thymocytes are hematopoietic progenitor cells present in the thymus. Into which cell type do thymocytes differentiate?

A

T-lymphocytes or T-cells

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8
Q

Name the region of an antibody responsible for binding to receptors on the surface of phagocytic cells

A

Fc region or Fc domain

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9
Q

Name the region of an antibody which binds to antigen

A

F(ab) region or F(ab) domain. Variable heavy and light chains would also be acceptable

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10
Q

The antigenic determinant bound by an antibody is known as the epitope. What name is given to the corresponding epitope-binding region on an antibody?

A

Paratope

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11
Q

The hypervariable loops in the VH and VL chains of the antigen-binding region of an antibody are known as what?

A

Complementarity Determining Regions

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12
Q

Which pathway of the Complement System is activated by antibody

A

Classical

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13
Q

Which evolutionary conserved family of proteins, considered functional ancestors of antibodies, are also able to activate the complement pathway identified in e)?

A

Pentraxins

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14
Q

What does NK stand for?

A

Natural Killer

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15
Q

From which lineage of the hematopoietic stem cell are NK cells derived?

A

Lymphoid lineage

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16
Q

To which arm of the immune system are NK cells considered to belong and why?

A

Innate, because they don’t require prior activation unlike B-cells and T-cells

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17
Q

Once activated to kill the target cell, the NK cell releases which two molecules ensuring the target cell is destined for death?

A

Granzymes and Perforins

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18
Q

Which other immune cell type uses the same mechanism for killing virus-infected or cancer cells?

A

Killer T-cells, CD8+ T-cells or Cytotoxin T-cells

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19
Q

What is the name of the procedure for the in vitro production of antibodies with pre-defined specificity?

A

Hybridoma technology

20
Q

Name the two scientists who pioneered the procedure of the in vitro production of antibodies with pre-defined specificity

A

George Kohler and Cesar Milstein

21
Q

From which secondary lymphoid organ are antibody-producing B cells extracted for fusion with myeloma cells following mouse immunisation?

A

Spleen

22
Q

In the table below, list 3 key properties each for myeloma cells and B cells which enable the production and selection of the hybrid antibody-producing cells

A

Myeloma cells:
property 1 - Infinite lifespan
Property 2 - Not able to produce antibody (Ig-)
property 3 - HGPRT -

B cells:
Property 1 - finite lifespan
property 2 -Capable of producing antibody (Ig+)
Property 3 - HGPRT+

23
Q

Following fusion of the B cells with the myeloma cells they are grown in which medium to allow selection of the immortilised antibody-producing hybrid cells?

A

Hypoxanthine-Aminopterin-Thymidine medium or HAT medium

24
Q

Name in full the component in the medium which blocks nucleic acid biosynthesis

A

Aminopterin

25
Q

The immunoglobulin (Ig) class secreted by Clone 1 is G3 (IgG3). Give the two possible molecular formulae for this IgG3 antibody molecule

A

y2k2

26
Q

The immunoglobulin class secreted by Clone 2 is M (IgM). Given that the molecular weight of a single Y-shaped Ig in an IgM molecule is 180kDa, what is the approximate molecular weight of an intact IgM molecule?

A

IgM molecules are pentamers comprising 5 Y-shaped Ig molecules so 5 x 180kDa = 900kDa

27
Q

The immunoglobulin class secreted by Clone 3 is A (IgA). Give the 3 possible valencies for an IgA antibody

A

2, 4 and 6

28
Q

To identify the many potential clones producing antibodies specific to antigen X (AgX), the culture fluids bathing the clones must be screened using a highthroughput immunoassay such as an ELISA. In the space below, draw an indirect Plate-Trapped-Antigen-ELISA showing: (1) antigen AgX, (2) anti-AgX antibody, and (3) anti-mouse secondary reporter molecule

A 
Substrate → Colour formation 
                    ↓
Anti-mouse enzyme conjugate 
                    ↓
          Anti-AgX mAb 
                    ↓
            Antigen AgX
29
Q

Give 2 examples of ligands that can be bound by the extracellular domains of TLRs

A

1) TLR1 - bound to ligand multiple triacyl lipopeptides located on bacteria
2) TLR3 - bound to dsRNA poly1:c located on viruses

30
Q

The binding of which ligand to TLR4 is enabled by MD-2?

A

Lipopolysaccharide

31
Q

In addition to ligand binding, why is TLR dimerization required?

A

To enable signalling via the intracellular signalling domain

32
Q

The signalling cascade, activated after TLR binding, results in the production of broad groups of molecules by the activated cell. Give two examples of these broad groups of molecules

A

Cytokines, chemokines, endothelial adhesion molecules, co-stimulatory molecules, type-1 interferons

33
Q

The figure below shows the antibody levels in the sera of groups of 6 sheep immunised with a toxoid alone, with toxoid in combination with an aluminium salt (alhydrogel), and with toxoid in combination with monophosphoryl lipid A (MPLA). Control animals were given phosphate buffered saline only (PBS).

A
  • Which group had the highest antibody titer? Toxoid + MPLA

-

34
Q

Both alhydrogel and MPLA boosted the antibody response. What name is given to these types of molecules that potentiate the immune response?

A

Adjuvants

35
Q

What is the most likely mechanism by which alhydrogel boosted the antibody response?

A

By forming a gel-like matrix and acting as a depot, then releasing antigen over a prolonged period

36
Q

What is the most likely mechanism by which MPLA boosted the antibody response?

A

By acting as an immune stimulator/modifier. MPLA is a Toll agonist, activating signalling pathways. This results in cytokine production which modifies the response.

37
Q

MPLA is derived from lipopolysaccharide (LPS). However, unlike LPS, MPLA shows low toxicity. What is the structural difference between LPS and MPLA that accounts for this reduction in toxicity?

A

MPLA lacks one of the phosphate groups of LPS

38
Q

Toxoid vaccines are in widespread use.

Name a disease that a toxoid vaccine can protect against?

A

Tetanus, diphtheria, anthrax, necrotic enteritis, enterotoxaemia, gas gangrene, botulism

39
Q

What is the nature of the protective immunity induced after vaccination with these toxoids?

A

Antibodies that neutralise the toxin

40
Q

Toxoid vaccines are traditionally prepared by treating the toxin with formaldehyde. How, at the molecular level, does this reduce toxicity of the toxin?

A

By creating intra- and inter-molecular linkages between molecules. Formaldehyde crosslinks amino groups in proteins with other nearby nitrogen atoms in proteins through a -CH2- linkage

41
Q

What is a modern alternative to formaldehyde treatment of toxins to create toxoids?

A

Genetic toxoids, where mutations are introduced into the encoding gene at triplets encoding functionally critical amino acids, to reduce toxicity

42
Q

Give 2 advantages of this technology compared to formaldehyde treatment?

A

Production in a harmless bacterium which allows:

  • Ease of production and high yield
  • Molecular structure more similar to the active toxin
  • Reproducible properties
  • No reversion
43
Q

The figure below shows two different antigen processing pathways.

Where would bacteria be located in the cell for bacterial proteins to be processed by the MHC I pathway?

A

Growing in the cytoplasm/cytosol

44
Q

How are proteins converted into peptide by the proteasome?

A

The proteasome has protease activities

45
Q

What is the consequence of peptide presentation to CD8+ T cells?

A

The CD8+ T-cells become primed to kill infected cells which display similar peptides on MHC Class I molecules

46
Q

Provide a consequence of peptide presentation to CD4+ T cells

A

The CD4+ T-cells produce cytokines that shape the immune response

47
Q

Which pathway would you expect to be activated if there is a strong antibody response to a bacterium?

A

The MHC Class II/ CD4+ T-cell pathway

Cellular basis of immunity extra (2 decks)

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