PCB 3323 Immunology Exam 3 Questions
and Answers Latest 2025 Top Rated
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.
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
μ heavy chains
surrogate light chains
lg alpha and Ig beta polypeptides
What do stromal cells provide developing B-cell?
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?
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?
2 for heavy
5 for light
What might happen if there wasn't allelic exclusion?
Fig. 6.8
No alleclic exclusion would give heterogeneous B cell
receptor with low avidity.
What does allelic exclusion mean and how is it
achieved?
means ensure that b-cell can make only one type of heavy
chain and one type of light-chain.
how is alleci exlusion achieve
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 ?
Transcription of RAG genes are turned off
,Are there any enzymes tagged for destruction to help
provide allelic exclusion?
RAG 2 is tagged for destruction
Which chain rearranges VDJ
H chain
Which chain rearrange V & J only?
L chain
Which are rearranged first, heavy, light, D-J or V-D?
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?
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?
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?
, 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?
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
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
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
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
and Answers Latest 2025 Top Rated
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.
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
μ heavy chains
surrogate light chains
lg alpha and Ig beta polypeptides
What do stromal cells provide developing B-cell?
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?
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?
2 for heavy
5 for light
What might happen if there wasn't allelic exclusion?
Fig. 6.8
No alleclic exclusion would give heterogeneous B cell
receptor with low avidity.
What does allelic exclusion mean and how is it
achieved?
means ensure that b-cell can make only one type of heavy
chain and one type of light-chain.
how is alleci exlusion achieve
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 ?
Transcription of RAG genes are turned off
,Are there any enzymes tagged for destruction to help
provide allelic exclusion?
RAG 2 is tagged for destruction
Which chain rearranges VDJ
H chain
Which chain rearrange V & J only?
L chain
Which are rearranged first, heavy, light, D-J or V-D?
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?
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?
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?
, 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?
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
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
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
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
