PCB 3233 Exam 4
What causes DiGeorge's syndrome? - correct answer ✔✔A deletion in chromosome 22 in which the
thymus fails to develop and T cells are absent.
thymus and aging - correct answer ✔✔-Thymus fully developed before birth; is most active in the young;
atrophies with age
*Progressively shrinks, fat gradually claiming areas once packed with thymocytes = involution of the
thymus
*Reduced production of new T cells not noticeably impairing T cell immunity
> Nor does thymectomy = removal of the thymus affect T cell immunity of adults
Life of T-Cell vs. Life of B-Cell - correct answer ✔✔T-Cell: once established the repertoire of mature
peripheral T cells is long lived and/or self-renewing
B-Cell: shorted lived cells that are continually being replenished from the bone marrow
Double-Negative (DN) thymocytes vs Double-Positive (DP) thymocytes - correct answer ✔✔DN-
no expression of CD4 or CD8.
Found in Thymus.
Cell Surface proteins- CD2,CD5
Notch 1- Keeps the T cell on the T cell path
DP-
Successful rearrangement of a beta-chain gene induces expression of the two co-receptors (CD4 & CD8).
You would find these in the inner cortex of the thymus.
, Which type of T cell receptor predominates αβ or γδ? - correct answer ✔✔The alpha:beta chain is
majority while the gamma:delta is minority
Which loci (α, β, γ, δ) begin their rearrangement roughly at the same time? - correct answer ✔✔The
beta, gamma, and delta chain genes in the thymocyte rearrange at the same time during the double
negative thymocyte production before the first checkpoint and after the committed double negative T-
cell progenitor.
What gene segments are rearranged for the alpha and beta chains? - correct answer ✔✔Alpha v,j. Beta
V,D and J are the gene segments that are rearrangement for the alpha and beta chain.
How many attempts can be performed at the β-chain locus in order to achieve a productive
rearrangement? Does the α-chain locus observe more attempts? - correct answer ✔✔-two attempts can
be made to achieve a production rearrangement of the B-chain locus on each homologous chromosome
(4 total)
-a-chain can sustain many attempts
Are the RAG genes used? Is the 12/23 rule observed? - correct answer ✔✔yes its is used.
12/23 rule is enforced at or prior to cleavage and support a synapsis model for V(D)J recombination.
What is pTα? What does it act as? Explain the involvement of the β-chain. - correct answer ✔✔-
surrogate alpha chain. signals cell to halt gamma, delta, Beta chains, gene rearrangement and begin
proliferation.
What makes up a pre-TCR. - correct answer ✔✔-surrogate alpha chain(pre-t alpha)
-b chain
-cd3 proteins( gamma:epsilon, epsilon:delta)
-zeta chain
pre-tcr involvement in b-chain - correct answer ✔✔The four signals for a Pre-TCR are stop Beta chain
arrangement (stop RAG 1 & 2), stimulate proliferation, express CD4 and CD8, and start alpha chain
arrangement
What causes DiGeorge's syndrome? - correct answer ✔✔A deletion in chromosome 22 in which the
thymus fails to develop and T cells are absent.
thymus and aging - correct answer ✔✔-Thymus fully developed before birth; is most active in the young;
atrophies with age
*Progressively shrinks, fat gradually claiming areas once packed with thymocytes = involution of the
thymus
*Reduced production of new T cells not noticeably impairing T cell immunity
> Nor does thymectomy = removal of the thymus affect T cell immunity of adults
Life of T-Cell vs. Life of B-Cell - correct answer ✔✔T-Cell: once established the repertoire of mature
peripheral T cells is long lived and/or self-renewing
B-Cell: shorted lived cells that are continually being replenished from the bone marrow
Double-Negative (DN) thymocytes vs Double-Positive (DP) thymocytes - correct answer ✔✔DN-
no expression of CD4 or CD8.
Found in Thymus.
Cell Surface proteins- CD2,CD5
Notch 1- Keeps the T cell on the T cell path
DP-
Successful rearrangement of a beta-chain gene induces expression of the two co-receptors (CD4 & CD8).
You would find these in the inner cortex of the thymus.
, Which type of T cell receptor predominates αβ or γδ? - correct answer ✔✔The alpha:beta chain is
majority while the gamma:delta is minority
Which loci (α, β, γ, δ) begin their rearrangement roughly at the same time? - correct answer ✔✔The
beta, gamma, and delta chain genes in the thymocyte rearrange at the same time during the double
negative thymocyte production before the first checkpoint and after the committed double negative T-
cell progenitor.
What gene segments are rearranged for the alpha and beta chains? - correct answer ✔✔Alpha v,j. Beta
V,D and J are the gene segments that are rearrangement for the alpha and beta chain.
How many attempts can be performed at the β-chain locus in order to achieve a productive
rearrangement? Does the α-chain locus observe more attempts? - correct answer ✔✔-two attempts can
be made to achieve a production rearrangement of the B-chain locus on each homologous chromosome
(4 total)
-a-chain can sustain many attempts
Are the RAG genes used? Is the 12/23 rule observed? - correct answer ✔✔yes its is used.
12/23 rule is enforced at or prior to cleavage and support a synapsis model for V(D)J recombination.
What is pTα? What does it act as? Explain the involvement of the β-chain. - correct answer ✔✔-
surrogate alpha chain. signals cell to halt gamma, delta, Beta chains, gene rearrangement and begin
proliferation.
What makes up a pre-TCR. - correct answer ✔✔-surrogate alpha chain(pre-t alpha)
-b chain
-cd3 proteins( gamma:epsilon, epsilon:delta)
-zeta chain
pre-tcr involvement in b-chain - correct answer ✔✔The four signals for a Pre-TCR are stop Beta chain
arrangement (stop RAG 1 & 2), stimulate proliferation, express CD4 and CD8, and start alpha chain
arrangement
