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Microbiology and Immunology 3300B Study Guide - Final Guide: Cytidine, Intron, Covalent Bond

Microbiology and Immunology
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Microimmune Lecture 9 Study Notes
1. When does development of the Ig chains take place?
First the J-D regions recombine, then the V with the DJ segments, then the light
chains can recombine. Light chains kappa and lamba do not recombine until the
heavy chains have.
2. What are immunoglobin isotopes?
We have many different forms of Ig that serve different functions. They are arranged
along a gene segment that looks like a bunch of exons and introns. IgM is always
first towards the 5’ end (human and mouse) and IgA is always towards the 3’ end.
Only difference is the number of Igs within the gene segment.
3. Discuss the J chain secrete form.
IgA can be secreted as dimeric held head to head by a J chain through non covalent
bonds. IgM can be secreted as a pentameric form through a J chain as well.
4. What are some immunoglobin functions?
IgM, IgG1/3 are good for activating the classical pathway. IgG1/3 are good for
placental transfer of nutrients. IgE is important in receruitment of mast
5. What receptors interact with the constant region of an antibody?
Fc receptors.
6. Why do we give so many doses of a vaccine?
Because the first doesn’t provoke a strong enough immune response.
7. What changes over the course of responses?
In the first response; there is a time lag, then a small increase with a plateau then a
general decline. In the second response there is a much greater efficiency and
effectiveness in immue response also built memory. This is the qualitiative change;
the quantitative change is that in the primary response IgG molecules are made, but
hten it switches to IgM to be more effective.
8. Where do point mutations mostly occur?
In the complimentary determining regions (CDR1/2/3) this is the molecular
structure within the variable regions that form the paratope.
9. What is somatic hypermutation?
Mutations are not occurring randomly; B cells target them specifically for the CDR
regions. The point mutations can be transitions or transversions and they are done
by AID (Activation Induced Cytadine Deaminase) in which it removes the amine
group from a cytidine and turns it into a uridine which is a non-coding nucleis acid.
This must be repaired.
10. What are the different pathways of repair?
Have a uridine repair mechanisms is what is making the mutations.
Miss match repair: MSH2/6 puts in an A or a T
Base Exision by UNG: C or G (leaves ribose)
Both of these are somatic hypermutations
After UNG aan also have APE can remove basic residues (ribose) to create a single
stranded nick gene conversion. This can lead to double stranded breaks which is
class switch recombination.