CMB2004 Exam Questions With Verified
Answers.
What is a pathogen? - answerA microorganism that causes disease e.g. bacteria, fungi, virus,
parasite
For an effective immune response the immune system must... - answer- be able to recognise
and respond to any invading organism
- not over react t...
What is a pathogen? - answer✔✔A microorganism that causes disease e.g. bacteria, fungi, virus,
parasite
For an effective immune response the immune system must... - answer✔✔- be able to recognise
and respond to any invading organism
- not over react to benign or self
- be able to direct different effector mechanisms against different pathogens
What is specific/adaptive immunity? - answer✔✔- it is induced by exposure to a particular
infection
- shows a high degree of specificity
- exhibits memory
What is the clonal selection theory? - answer✔✔1. Removal of potentially self reactive immature
lymphocytes by clonal selection
2. Pool of mature naive lymphocytes
3. Proliferation and differentiation of activated specific lymphocytes to form a clone of effector
cells
What are BCRs and what do they do? - answer✔✔B cell receptor expressed by B lymphocytes is
subsequently secreted when B cell is activated now known as an antibody
What is the structure of an antibody? - answer✔✔
What is the function of a T cell receptor? - answer✔✔- Unlike antibody, it doesn't bind free
antigen
- Binds/recognises processed antigen
- Presented in the cleft/binding groove of MHC class I or class II molecules
What are MHC molecules? - answer✔✔major histocompatibility complex molecules, also called
HLA (human leukocyte antigens)
a collection of cell surface markers that identify the cells as self
Rearrangement of Ig genes - answer✔✔- Genes rearrange during B cell development to form a
functional gene
- Production of functional immunoglobulin genes involves recombination to bring gene segments
together
- After DNA breaks, a single V and a single J gene segment are joined together to encode the V
region of the light chain
- Similarly, a single V, D and J gene segment are joined together in a single B cell to encode the
V region
Types of segments in heavy and light chains - answer✔✔V - variable
D - diversity
J - joining
C - constant
Hierarchy of rearrangements - answer✔✔- greater variability in heavy chains as V, D and J
- first heavy chain genes (D-J then V-D)
- then light chains genes; kappa first (V-J)
- if kappa rearrangement is unsuccessful then lama genes rearrange
What are recombination signal sequences? - answer✔✔Conserved sequences of non coding
DNA that are recognised by the RAG1/RAG2 enzyme complex during V(D)J recombination in
immature B and T cells
5 mechanisms for the generation of antibody diversity - answer✔✔1) Multiple gremlins genes -
multiple VH, Vkappa, Vlambda
2) Combinational diversity - different V, D and J segments to recombine to produce different
sequences
3) Junctional diversity - imprecise joining, N regions
4) Combinations of heavy and light chains
5) Somatic hypermutation - mutation frequency in antibody Vhgenes orders of magnitude higher
than normal spontaneous mutation rate, occurs in germinal centres as B cells recognised Ag and
proliferates, involves the enzyme AID which acts on DNA to de-animate cytosine to uracil ,
which is then recognises by error prone DNA repair pathways leading to mutations
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