PCB 3233: IMMUNOLOGY, EXAM 4 QUESTIONS
2 Distinct T-Cell Lineages - Answer -a:b & g:d (α:β & γ:δ)
Positive Selection - Answer -leads to the death of immature T-cells having receptors
that do not interact with any self-MHC I or II (takes place prior to negative selection)
Negative Selection - Answer -induces death of those immature T-cells that are
autoreactive (also happens with B-cells)
Majority Lineage Type of T-Cell - Answer -a:b (α:β 95%)
Minority Lineage Type of T-Cell - Answer -g:d (γ:δ 5%)
What is another word for immature T-cell? - Answer -thymocyte
What is the epithelial cell network that thymocytes are embedded in called? - Answer -
thymic stroma
What takes place in the Thymus Cortex? - Answer -most of T-cell maturation (except
negative selection)
What takes place in the Thymus Medulla? - Answer -negative selection of T-cells
What do macrophages in the cortex and medulla do? - Answer -remove thymocytes
that fail to mature properly
What are Hassall's corpuscles? - Answer -a feature of the medulla; site of cell
destruction
What is DiGeorge syndrome? - Answer -deletion of chromosome 22; thymus fails to
develop
Progenitor T-Cell - Answer -lack the cell surface glycoproteins (have CD34 surface
glycoprotein of stem cells), germline configuration
Double Negative Thymocyte - Answer -at the start of gene rearrangement; no CD4 or
CD8
Double Positive Thymocyte - Answer -after rearrangement; expresses both CD4 and
CD8
Single Positive Thymocyte - Answer -after positive selection; expresses CD4 or CD8
, IL-7 Receptor - Answer -essential for binding IL-7 secreted by thymic stromal cells;
helps tell the cell what to do next
Notch-1 - Answer -at all stages of maturation in the thymus signals are sent to this
receptor to drive the T-cell in their differentiation
How many chances (per chromosome) does the B-chain have to rearrange productivly?
- Answer -2
What does a successful rearrangement of the B-chain induce? - Answer -expression of
CD4 and CD8
Allelic Exclusion of B-chain - Answer -proliferation initiated by signaling is repressed
What signals are repressed in allelic exclusion of the B-chain? - Answer -pre-TCR,
RAG-1, RAG-2
When does rearrangement of the a-chain occur? - Answer -after the double-positive
cells stop dividing
Will most developing T-cell be able to make a productive a-chain rearrangement? -
Answer -yes
What happens after the first rearrangement between V and J segments on the a-chain?
- Answer -d (δ) segment is deleted
What is the first checkpoint of a:b (α:β) chain rearrangement? - Answer -once a b-chain
is produced it is sent to the ER to make sure it can bind to the surrogate a-chain (pTα)
What is the second checkpoint of a:b (α:β) chain rearrangement? - Answer -once an a-
chain is made it is sent to the ER to make sure it can bind to the b-chain
How many MHC molecules does an individual express? - Answer -12 (6 MHC-I and 6
MHC-II)
What percentage of a:b (α:β) TCRs will pass positive selection? - Answer -1-2%
Can molecules fail positive selection for recognizing too strongly? - Answer -yes
Can molecules fail positive selection for recognizing too weakly? - Answer -yes
Where does positive selection take place? - Answer -cortex of thymus
Which region codes for CDR1 and CDR2? - Answer -V region
What recognizes MHC in positive selection? - Answer -CDR1 and CDR2
2 Distinct T-Cell Lineages - Answer -a:b & g:d (α:β & γ:δ)
Positive Selection - Answer -leads to the death of immature T-cells having receptors
that do not interact with any self-MHC I or II (takes place prior to negative selection)
Negative Selection - Answer -induces death of those immature T-cells that are
autoreactive (also happens with B-cells)
Majority Lineage Type of T-Cell - Answer -a:b (α:β 95%)
Minority Lineage Type of T-Cell - Answer -g:d (γ:δ 5%)
What is another word for immature T-cell? - Answer -thymocyte
What is the epithelial cell network that thymocytes are embedded in called? - Answer -
thymic stroma
What takes place in the Thymus Cortex? - Answer -most of T-cell maturation (except
negative selection)
What takes place in the Thymus Medulla? - Answer -negative selection of T-cells
What do macrophages in the cortex and medulla do? - Answer -remove thymocytes
that fail to mature properly
What are Hassall's corpuscles? - Answer -a feature of the medulla; site of cell
destruction
What is DiGeorge syndrome? - Answer -deletion of chromosome 22; thymus fails to
develop
Progenitor T-Cell - Answer -lack the cell surface glycoproteins (have CD34 surface
glycoprotein of stem cells), germline configuration
Double Negative Thymocyte - Answer -at the start of gene rearrangement; no CD4 or
CD8
Double Positive Thymocyte - Answer -after rearrangement; expresses both CD4 and
CD8
Single Positive Thymocyte - Answer -after positive selection; expresses CD4 or CD8
, IL-7 Receptor - Answer -essential for binding IL-7 secreted by thymic stromal cells;
helps tell the cell what to do next
Notch-1 - Answer -at all stages of maturation in the thymus signals are sent to this
receptor to drive the T-cell in their differentiation
How many chances (per chromosome) does the B-chain have to rearrange productivly?
- Answer -2
What does a successful rearrangement of the B-chain induce? - Answer -expression of
CD4 and CD8
Allelic Exclusion of B-chain - Answer -proliferation initiated by signaling is repressed
What signals are repressed in allelic exclusion of the B-chain? - Answer -pre-TCR,
RAG-1, RAG-2
When does rearrangement of the a-chain occur? - Answer -after the double-positive
cells stop dividing
Will most developing T-cell be able to make a productive a-chain rearrangement? -
Answer -yes
What happens after the first rearrangement between V and J segments on the a-chain?
- Answer -d (δ) segment is deleted
What is the first checkpoint of a:b (α:β) chain rearrangement? - Answer -once a b-chain
is produced it is sent to the ER to make sure it can bind to the surrogate a-chain (pTα)
What is the second checkpoint of a:b (α:β) chain rearrangement? - Answer -once an a-
chain is made it is sent to the ER to make sure it can bind to the b-chain
How many MHC molecules does an individual express? - Answer -12 (6 MHC-I and 6
MHC-II)
What percentage of a:b (α:β) TCRs will pass positive selection? - Answer -1-2%
Can molecules fail positive selection for recognizing too strongly? - Answer -yes
Can molecules fail positive selection for recognizing too weakly? - Answer -yes
Where does positive selection take place? - Answer -cortex of thymus
Which region codes for CDR1 and CDR2? - Answer -V region
What recognizes MHC in positive selection? - Answer -CDR1 and CDR2
