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PCB 3233 ch 6, PCB 3323 Immunology Exam 3 questions well answered
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PCB 3233 ch 6, PCB 3323 Immunology Exam 3 questions well answered
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PCB 3233 ch 6, PCB 3323 ImmunologyExam 3
Pre-B cell receptor, there are several things taking place in the B cell at this point, what are they? What
makes up the pre-B cell receptor? Example; allelic exclusion. - correct answer ✔✔Pre B-cell is entering
checkpoint one, and has a surrogate light chain attach to its recombined heavy chain to ensure the heavy
chain is function. Cell is also growing in size to divide into several small B-cells
what makes up the pre-B cell receptor - correct answer ✔✔μ heavy chains
surrogate light chains
lg alpha and Ig beta polypeptides
What do stromal cells provide developing B-cell? - correct answer ✔✔Bone marrow stromal cells
provide specialize environment for B cells at various stages of maturation
1. Make specific cell-surface contacts with B cells
− Stem cells and early pro-B cells use the integrin VLA-4 to
bind to the adhesion molecule VCAM-1 on stromal cells 2. Produce growth factors that act on bound B
cells
− Interactions between other cell adhesion molecules (cams) promote the binding of the receptor Kit on
the B cell to stem-cell factor (SCF) on the stromal cell
− Activation of Kit causes the B cell to proliferate
− B cells at later stage of maturation require interleukin-7 (IL- 7) to stimulate their growth and
proliferation
What does IL-7 do and when/where is it needed in B-cell development? - correct answer ✔✔is another
growth factor enhancing growth and proliferation during later stage of late pro- B cell maturation.
How many chances does a cell have to make a functional heavy chain rearrangement? Does the light
chain have more chances than the heavy chain? - correct answer ✔✔2 for heavy
,5 for light
What might happen if there wasn't allelic exclusion? Fig. 6.8 - correct answer ✔✔No alleclic exclusion
would give heterogeneous B cell receptor with low avidity.
What does allelic exclusion mean and how is it achieved? - correct answer ✔✔means ensure that b-cell
can make only one type of heavy chain and one type of light-chain.
how is alleci exlusion achieve - correct answer ✔✔successful gene rearrangement is signaled by the
appearance of the protein product of the gene at the cell surface by Ig alpha and Ig beta
What genes are turned off during allelic exclusion ? - correct answer ✔✔Transcription of RAG genes are
turned off
Are there any enzymes tagged for destruction to help provide allelic exclusion? - correct answer ✔✔RAG
2 is tagged for destruction
Which chain rearranges VDJ - correct answer ✔✔H chain
Which chain rearrange V & J only? - correct answer ✔✔L chain
Which are rearranged first, heavy, light, D-J or V-D? - correct answer ✔✔1. Heavy - DJ
2. Heavy - VDJ
3. Light - VJ
Surrogate light chain, 5 and VpreB. What each subunit substitutes for, when and where is this
happening? Why do you need this subunit produced? Is this one of the checkpoints during maturation? -
correct answer ✔✔1. Lambda 5 subs for C region
2. VpreB subs for v region
3. This is occurring in the bone marrow in large pre-B-cells. You need this subunit produced to ensure
that the newly recombined heavy chain can work with a light chain.
4. This is checkpoint 1.
, Igalpha and Igbeta, what do these do and when would you expect to see them expressed? - correct
answer ✔✔1. Tail is not long enough on BCR so they help signal to stop rearrangement
2. You see them expressed during pre-b cell stage
Immature B cell vs. mature B cell, are there differences? - correct answer ✔✔1. Immature only has IgM
on surface.
2. Mature has IgM and IgD
Large Pre-B cell ---> Small Pre-B cell, what significant happens or is formed at this point in B cell
maturation? - correct answer ✔✔1. Associated with rearrangement of Ig light chain.
Light chain begins productin and large B-cell divides into several small pre B-cells.
Clonal deletion - correct answer ✔✔is the selective death of lymphocytes that are either autoreactive
(light chain rearrangements fail to produce non-self reactive receptors) or fail to make a functional
immunoglobulin.
Anergy - correct answer ✔✔is a state of developmental arrest that occurs when B cells are specific for
monovalent self-antigens. These cells are not signaled to rearrange light chain genes or undergo
apoptosis, but are simply inactivated and become unresponsive to Ag. IgM is not functional and cell has
a shortened life span. Cells do enter circulation
Development of B cells, where and steps and names. Ex; early pro-B cell - correct answer ✔✔PRO comes
before PRE
LARGE comes before SMALL
Signal for successful gene rearrangement (checkpoints), what happens if the cell fails the checkpoint and
what would cause it to fail at the checkpoint - correct answer ✔✔After V D and J- ligand checks heavy
chain and signal to stop rearrangement
After light chain-> check for BCR-> prevents apoptosis and starts proliferation
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