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PCB 3233 Exam 4 Study Guide questions with complete solutions
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PCB 3233 Exam 4 Study Guide questions with complete solutions
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PCB 3233 Exam 4 Study Guidestart of chapter 7
Where does T-cell maturation take place? - correct answer ✔✔T-cell maturation takes place in the
thymus
Be able to understand some similarities and differences between B cell and T cell development.
a. Examples: Where do they derive? What cellular mechanisms or processes are shared between the
two? What comprises their cell lineages? - correct answer ✔✔Both B-cells and T-cells derive from the
bone marrow stem cells but the T-cell moves to the thymus to mature while the B-cell stays in the bone
marrow. Both undergo gene rearrangement which produces antigen receptors. T cells have two lineages.
Regarding the initial stages of T-cell maturation, explain the direction of its migration using "subcapsular
region", "medulla", and "cortex" as references in your description. Where would you expect to find
macrophages? What about dendritic cells? - correct answer ✔✔As the T-cell matures, it migrates from
the subcapsular region of the thymus to the inner cortex and to the medulla. Macrophages are found in
both the cortex and the medulla. Dendritic cells are found in the medulla.
In the thymus, what is the role of macrophages? Where are Hassal's corpuscles found? - correct answer
✔✔Macrophages remove the thymocytes that do not mature properly. Hassal's corpuscles is found in
the medulla of the thymus and it induces the development of regulatory T cells.
Evident from patient's who demonstrate DiGeorge's syndrome, the development of a functional T-cell
repertoire is crucial to an individual's health. What causes DiGeorge's syndrome? Know the chromosome
affected. Identify what is NOT being produced in this clinical condition, and what further consequences
are associated. Can DiGeorge's syndrome be cured? - correct answer ✔✔DiGeorge's syndrome is caused
by a deletion in chromosome 22 where the thymus fails to develop and T cells are absent. The lack of T
cells and thymus increases susceptibility to a wide range of opportunistic infections and it resembles
SCID (severe combined immunodeficiency disease). Cannot be cured.
The thymus is considered to be completely developed before birth. However, its deterioration results
with natural aging, indicating that the younger you are, the more active it is. Knowing this, would you
expect T-cell immunity to become defective overtime? Why or why not? What about in the case of a
, thymectomy (removal of thymus); would you expect impairment then? - correct answer ✔✔T-cell
immunity does not become defective over age. The thymus just does not develop as many T-cells over
time. T-cells stay in circulation for several years. T-cells do not become defective even after a
thymectomy.
How does the life of a T cell differ from that of a B cell? Which lives longer and why do you think that is?
(Hint: understand what "self renewing" means in this context) - correct answer ✔✔T cells are long-lived
and self-renewing. T cells are in circulation in the blood stream for several months. Self-renewing cells
divide to maintain the amount of cells.
Double-Negative (DN) thymocytes vs. Double-Positive (DP) thymocytes:
a. When/why are they called DN thymocytes?
i) What cell-surface proteins are expressed? Which are NOT being expressed?
ii) What is the importance of Notch 1 for these thymocytes?
b. When/why are they called DP thymocytes?
i) What cell-surface proteins are being expressed at this point? - correct answer ✔✔a. T cells that
express the αβ TCR but do not express CD4/CD8/NK cell markers. This happens when the progenitor T
cell expresses T-cell specific adhesion molecule CD2 and other molecules but not TCR complex.
i) CD2 and CD5 are expressed. CD4 and CD8 are not expressed.
ii) Notch 1 keeps the T-cell on the T-cell path.
b. T cells that express both CD4 and CD8.
i) CD2, CD5, CD4, and CD8 are being expressed.
The two T-cell lineages: α:β and γ:δ
a. Which is considered to be the majority and which is the minority?
b. Do the loci lineages derive from a common DN or DP thymocyte precursor?
c. Which loci (α, β, γ, δ) begin their rearrangement roughly at the same time?
i) Understand what is meant by "competition" that's observed at this point, and what will be produced
as an outcome. (Hint: depends on what T-cell lineage is made, think about what the result would be if a
β chain was made before γδ; what is more frequent outcome? - correct answer ✔✔a. α:β is the majority
and γ:δ is the minority.
b. Both α:β and γ:δ derive from double negative thymocyte precursor.
c. α, γ, and δ rearrange at about the same time.
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