Extra Flashcards
In which system of the body does dendritic cell activation of B cells occur?
In the lymphatic system (you can be more specific than this e.g. within the germinal centres)
The antigen binding receptor on the surface of a B cell is comprised of what?
Antibody
Which sub-set of helper T cells has a cytokine profile that stimulates B cell antibody production?
TH2
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
- Dectin-1
- Dectin-2
- Mincle
B cells are derived from which lineage of the hematopoietic stem cell?
Lymphoid
A mature B cell that hasn’t yet encountered antigen is referred to as what?
Naïve
Thymocytes are hematopoietic progenitor cells present in the thymus. Into which cell type do thymocytes differentiate?
T-lymphocytes or T-cells
Name the region of an antibody responsible for binding to receptors on the surface of phagocytic cells
Fc region or Fc domain
Name the region of an antibody which binds to antigen
F(ab) region or F(ab) domain. Variable heavy and light chains would also be acceptable
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?
Paratope
The hypervariable loops in the VH and VL chains of the antigen-binding region of an antibody are known as what?
Complementarity Determining Regions
Which pathway of the Complement System is activated by antibody
Classical
Which evolutionary conserved family of proteins, considered functional ancestors of antibodies, are also able to activate the complement pathway identified in e)?
Pentraxins
What does NK stand for?
Natural Killer
From which lineage of the hematopoietic stem cell are NK cells derived?
Lymphoid lineage
To which arm of the immune system are NK cells considered to belong and why?
Innate, because they don’t require prior activation unlike B-cells and T-cells
Once activated to kill the target cell, the NK cell releases which two molecules ensuring the target cell is destined for death?
Granzymes and Perforins
Which other immune cell type uses the same mechanism for killing virus-infected or cancer cells?
Killer T-cells, CD8+ T-cells or Cytotoxin T-cells
What is the name of the procedure for the in vitro production of antibodies with pre-defined specificity?
Hybridoma technology
Name the two scientists who pioneered the procedure of the in vitro production of antibodies with pre-defined specificity
George Kohler and Cesar Milstein
From which secondary lymphoid organ are antibody-producing B cells extracted for fusion with myeloma cells following mouse immunisation?
Spleen
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
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+
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?
Hypoxanthine-Aminopterin-Thymidine medium or HAT medium
Name in full the component in the medium which blocks nucleic acid biosynthesis
Aminopterin
The immunoglobulin (Ig) class secreted by Clone 1 is G3 (IgG3). Give the two possible molecular formulae for this IgG3 antibody molecule
y2k2
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?
IgM molecules are pentamers comprising 5 Y-shaped Ig molecules so 5 x 180kDa = 900kDa
The immunoglobulin class secreted by Clone 3 is A (IgA). Give the 3 possible valencies for an IgA antibody
2, 4 and 6
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
Substrate → Colour formation
↓
Anti-mouse enzyme conjugate
↓
Anti-AgX mAb
↓
Antigen AgXGive 2 examples of ligands that can be bound by the extracellular domains of TLRs
1) TLR1 - bound to ligand multiple triacyl lipopeptides located on bacteria
2) TLR3 - bound to dsRNA poly1:c located on viruses
The binding of which ligand to TLR4 is enabled by MD-2?
Lipopolysaccharide
In addition to ligand binding, why is TLR dimerization required?
To enable signalling via the intracellular signalling domain
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
Cytokines, chemokines, endothelial adhesion molecules, co-stimulatory molecules, type-1 interferons
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).
- Which group had the highest antibody titer? Toxoid + MPLA
-
Both alhydrogel and MPLA boosted the antibody response. What name is given to these types of molecules that potentiate the immune response?
Adjuvants
What is the most likely mechanism by which alhydrogel boosted the antibody response?
By forming a gel-like matrix and acting as a depot, then releasing antigen over a prolonged period
What is the most likely mechanism by which MPLA boosted the antibody response?
By acting as an immune stimulator/modifier. MPLA is a Toll agonist, activating signalling pathways. This results in cytokine production which modifies the response.
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?
MPLA lacks one of the phosphate groups of LPS
Toxoid vaccines are in widespread use.
Name a disease that a toxoid vaccine can protect against?
Tetanus, diphtheria, anthrax, necrotic enteritis, enterotoxaemia, gas gangrene, botulism
What is the nature of the protective immunity induced after vaccination with these toxoids?
Antibodies that neutralise the toxin
Toxoid vaccines are traditionally prepared by treating the toxin with formaldehyde. How, at the molecular level, does this reduce toxicity of the toxin?
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
What is a modern alternative to formaldehyde treatment of toxins to create toxoids?
Genetic toxoids, where mutations are introduced into the encoding gene at triplets encoding functionally critical amino acids, to reduce toxicity
Give 2 advantages of this technology compared to formaldehyde treatment?
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
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?
Growing in the cytoplasm/cytosol
How are proteins converted into peptide by the proteasome?
The proteasome has protease activities
What is the consequence of peptide presentation to CD8+ T cells?
The CD8+ T-cells become primed to kill infected cells which display similar peptides on MHC Class I molecules
Provide a consequence of peptide presentation to CD4+ T cells
The CD4+ T-cells produce cytokines that shape the immune response
Which pathway would you expect to be activated if there is a strong antibody response to a bacterium?
The MHC Class II/ CD4+ T-cell pathway
