PCB 3233 EXAM 4 QUESTIONS & ANSWERS
What causes DiGeorge's syndrome? - Answer -A deletion in chromosome 22 in which
the thymus fails to develop and T cells are absent.
thymus and aging - 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 - 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 - 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? - 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? - 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? - 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? - Answer --
What causes DiGeorge's syndrome? - Answer -A deletion in chromosome 22 in which
the thymus fails to develop and T cells are absent.
thymus and aging - 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 - 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 - 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? - 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? - 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? - 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? - Answer --
