Extra

Question 1

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

Answer 1

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

Question 2

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

Answer 2

Antibody

Question 3

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

Answer 3

TH2

Question 4

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

Answer 4

• Dectin-1
• Dectin-2
• Mincle

Question 5

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

Answer 5

Lymphoid

Question 6

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

Answer 6

Naïve

Question 7

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

Answer 7

T-lymphocytes or T-cells

Question 8

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

Answer 8

Fc region or Fc domain

Question 9

Name the region of an antibody which binds to antigen

Answer 9

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

Question 10

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?

Answer 10

Paratope

Question 11

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

Answer 11

Complementarity Determining Regions

Question 12

Which pathway of the Complement System is activated by antibody

Answer 12

Classical

Question 13

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

Answer 13

Pentraxins

Question 14

What does NK stand for?

Answer 14

Natural Killer

Question 15

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

Answer 15

Lymphoid lineage

Question 16

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

Answer 16

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

Question 17

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

Answer 17

Granzymes and Perforins

Question 18

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

Answer 18

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

Question 19

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

Answer 19

Hybridoma technology

Question 20

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

Answer 20

George Kohler and Cesar Milstein

Question 21

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

Answer 21

Spleen

Question 22

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

Answer 22

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+

Question 23

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?

Answer 23

Hypoxanthine-Aminopterin-Thymidine medium or HAT medium

Question 24

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

Answer 24

Aminopterin

Question 25

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

Answer 25

y2k2

Question 26

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?

Answer 26

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

Question 27

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

Answer 27

2, 4 and 6

Question 28

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

Answer 28

``` Substrate → Colour formation ↓ Anti-mouse enzyme conjugate ↓ Anti-AgX mAb ↓ Antigen AgX ```

Question 29

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

Answer 29

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

Question 30

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

Answer 30

Lipopolysaccharide

Question 31

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

Answer 31

To enable signalling via the intracellular signalling domain

Question 32

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

Answer 32

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

Question 33

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).

Answer 33

- Which group had the highest antibody titer? Toxoid + MPLA | -

Question 34

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

Answer 34

Adjuvants

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

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?

Answer 37

MPLA lacks one of the phosphate groups of LPS

Question 38

Toxoid vaccines are in widespread use. Name a disease that a toxoid vaccine can protect against?

Answer 38

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

Question 39

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

Answer 39

Antibodies that neutralise the toxin

Question 40

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

Answer 40

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

Question 41

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

Answer 41

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

Question 42

Give 2 advantages of this technology compared to formaldehyde treatment?

Answer 42

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

Question 43

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?

Answer 43

Growing in the cytoplasm/cytosol

Question 44

How are proteins converted into peptide by the proteasome?

Answer 44

The proteasome has protease activities

Question 45

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

Answer 45

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

Question 46

Provide a consequence of peptide presentation to CD4+ T cells

Answer 46

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

Question 47

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

Answer 47

The MHC Class II/ CD4+ T-cell pathway