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CMB2004 FINAL EXAM; QUESTIONS AND VERIFIED ANSWERS
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CMB2004 FINAL EXAM; QUESTIONS ANDVERIFIED ANSWERS
What are the 4 sources of infection? - ANSWER Bacteria, viruses, fungi, parasites
What does the immune system need to be able to do for an effective immune
response? - ANSWER 1- Be able to recognise and respond to any invading
organism
2- Not over react to benign or self
3- Be able to direct different effector mechanisms against different pathogens
approximately how many bacteria are their and how many are named? - ANSWER
10^9 bacteria and 30000 named
What is specific/adaptive immunity? - ANSWER It is induced by exposure to a
particular infection, it shows a high degree of specificity and exhibits memory
How is specific immunity mediated? - ANSWER BY B/T lymphocytes with
clonally distributed receptors, this is a large repertoire but low frequency of cells
for one specific antigen
Is specific immunity slow or fast to develop? - ANSWER Slow but quicker the
second time
What is clonal selection theory? - ANSWER The clonal selection theory is that one
individual cell is selected, by virtue of its ability to recognize an antigen, to make
billions of clones of itself to help the body rid itself of one particular pathogen.
When B-cells undergo clonal selection, most clones becomes plasma cells which
will produce massive amounts of antibody against the particular antigen invading
the body, after the pathogens have been removed from the body, the plasma cells
will undergo apoptosis and die.
What happens when a B cell is activated? - ANSWER After something has bound
the the antigen binding site, the membrane form of immunoglobulin is released and
is known as an antibody
,What do T cells recognise? - ANSWER Only A short peptide fragment
What is the difference between TCR and BCR? - ANSWER TCR is never secreted
and it needs the peptide fragments to be presented to it.
What do antibodies do? - ANSWER Infection with encapsulated bacteria
Activation of complement by opsonization or classical and MAC pathways
Activation of effector cells
What is the structure of antibodies? - ANSWER Basic 4 chain structure
2 identical heavy and light chains held together by covalent and non covalent bonds
2 types of light chain A and K
Each chain has a variable and constant region
Antigen binding sites have a VH and VL regions
Different CH regions interact with complement and the Fc region binds to different
FcRs expressed by the effector cells.
What is responsible for the AB structure in antibodies? - ANSWER The constant
regions are responsible for both AB structure and interacting with other molecules
and cells of the innate system
What are the 5 classes of Antibodies? - ANSWER IgM D A G and E
What determines the isotype of an antibody? - ANSWER Isotypes are determined
by the heavy chain
How does Antigen interaction work? - ANSWER Through the variable region
which is specific for each given Ab with concentrated regions of variability. There
is hypervariable regions and 6 hypervariable loops which lead to the antigen
binding site. Both heavy and light chains contribute. The Ag binds to an aa in
CDRs.
What is an antigen epitope? - ANSWER the part of an antigen that is recognised by
the immune system, if continuous it means it binds on a continuous part of the
structure, they can also be non-linear and not be connected.
,How does antigen recognition work? - ANSWER Epitopes recognised by
antibodies can be continuous or conformational.
Ag can be almost any molecule
Antibody and Ag form non-covalent interactions
Ag sequence may be manipulated in vaccine designs
Ag may be folded
DRs present in antibody V regions determine the specificity and the affinity of an
antibody for Ag
What does A T cell receptor do? - ANSWER It doesn't bind to free antigen, binds
to processed antigen, presented in the cleft of MHC class I or class II molecules. It
is never secreted
TCR structure - ANSWER Heterodimer (TCR alpha and TCR beta) joined by a
disulfide bond. Each chain has a constant and a variable region. V domains interact
with antigen.
What are the classes of MHC molecules and where are they expressed? - ANSWER
Class1- Expressed by nearly all cell types
Class 2- Expression restricted to a specialised group of immune cells
What is the differences between MHC class 1 and 2. - ANSWER Different
structures, Class 1 has 3 alpha 1 beta class 2 has 2 of each.
Different expression patterns
Present peptides from different sources
Essential in transplant rejection
What are the three different MHC class 1 molecules? - ANSWER HLA-1A HLA-B
AND HLA-C
How is MHC class 1 structures formed? - ANSWER A 1 and A2 domains fold to
form B sheet known as peptide binding site.
DNA encoding a1 and a2 domains is very polymorphic
, a3 domain fold into Ig like domains
How is MHC class 2 structures formed? - ANSWER Expression limited to APC.
Heterodimers and the alpha and beta domains are a similar size
3 different molecules. More open than groove
What genes encode a single polypeptide chain? - ANSWER H chain and TCRb, V
region is encoded by three gene segments V D and J with V as the biggest
L chain and TCRa, v region encoded by two gene segments V and J
Where are Ig genes found? - ANSWER In the genome as families of gene segments
What happens in B cells regarding the Ig gene? - ANSWER During development in
the bone marrow the DNA containing the Ig gene segments is deliberately broken
and the gene segments are rearranged. Each B cell performs the breakage and
rearrangement randomly.
What joins after B cell DNA is broken produce a functional Ig gene? - ANSWER A
single V and Single J gene segment are joined together to encode the V region of
the light chain. A single random V D and J gene segment are joined to encode the
V region of the Heavy Chain. Leads to a random heavy and light chain region
What is the order that B cell development Ig rearrangements occur in? - ANSWER
First H chain gene segments rearrange, D-J then V-DJ, then light chain gene
segments rearrange, V-J first, if kappa light chain fails then alpha gene V-J
rearrange.
What are the 5 key things in the recombination process? - ANSWER 1- Ig gene
segment rearrangement is guided by special sequences flanking each of the V D
and J gene segments, RSS
2-Rearrangement involves a complex of enzymes
3-Recombination activating gene
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