PCB4233 Immunology Final Exam
What are the three signals required for T cell activation? - CORRECT ANSWER-1.
TCR signaling
2. Costimulatory interaction
3. Cytokine signaling (ex. autocrine and paracrine IL-2)
What cytokine is important for T cell activation? - CORRECT ANSWER-IL-2
Why are alpha beta T cells CD3+ and gamma delta T cells CD3-? - CORRECT
ANSWER-CD3 is responsible for antigen-MHC T cell activation and gamma delta T
cells do not require the MHC for T cell activation
What is the Src family? - CORRECT ANSWER-A family of tyrosine kinases that
contains 6 conserved domains, including SH2 and SH3. Src family kinases play a
role during T cell activation
Describe the first phase of T cell activation - CORRECT ANSWER-1. TCR engages
with MHCII (or MHCI)
2. CD4 (or CD8) stabilizes the interaction
3. CD45 activates Lck on CD4 (or CD8)
4. Lck phosphorylates ITAMs found on CD3 (gamma, delta, epsilon, zeta chains)
5. ZAP-70 uses SH2 domain to dock to ITAMs
6. ZAP-70 phosphorylates LAT (linker protein of activated T cells) and SLP-76
Describe positive selection - CORRECT ANSWER-MHC is presented to naive T
cells. T cells which bind well to MHC are positively selected for. If there is weak
binding, the cell undergoes apoptosis (programmed cell death). If the cell binds
strongly to MHCII, the cell upregulates ThPOK and downregulates Runx3 to
become a CD4+ T cell. Otherwise, the cell becomes a CD8+ T cell
ThPOK+Runx3- - CORRECT ANSWER-CD4+ T cell
ThPOK-Runx3+ - CORRECT ANSWER-CD8+ T cell
Describe negative selection - CORRECT ANSWER-If a T cell binds too strongly to
MHC, the cell undergoes apoptosis
Why is negative selection important? - CORRECT ANSWER-It is a measure to
protect against autoimmunity
, How does negative selection ensure T cells don't respond inappropriately to
peptide-MHC complexes not found in the thymus? - CORRECT ANSWER-AIRE is
a protein that induces expression of proteins not found in the thymus, ex. lung
protein, to ensure that T cells do not react to proteins found throughout the body
after undergoing negative selection
How do T cells move through the thymus? - CORRECT ANSWER-1. Arrive to
thymus via corticomedullary junction
2. Differentiate into T cells in thymic epithelium
3. Move into thymic cortex where they proliferate and express TCR
4. Selection process
5. Move to thymic medulla
6. Leave via corticomedullary junction
What is the role of Bcl-2? - CORRECT ANSWER-Prevents apoptosis by inhibiting
Bax and Bak
What is the function of Bax and Bak? - CORRECT ANSWER-Open mitochondrial
membrane, releasing cytochrome C, triggering apoptosis
What is the function of Fas? - CORRECT ANSWER-Induces apoptosis
How does the signal from an antigen influence T cell survival? - CORRECT
ANSWER-Antigen signal prevents apoptosis by upregulating Bcl-2, without a
signal from antigen, T cells downregulate Bcl-2, leading to apoptosis as a
protection measure against autoimmunity
What ligand determines whether bone marrow stem cells will differentiated in B
cells or T cells? - CORRECT ANSWER-Notch, Notch positive cells become T cells
while Notch negative cells become B cells
Bone marrow stem cells exposed to Notch will become - CORRECT ANSWER-T
cells
Where are Notch ligands found? - CORRECT ANSWER-The thymic epithelium
Which process is responsible for driving CD4 or CD8 expression? - CORRECT
ANSWER-Positive selection
Where do lymphocytes reach maturity? - CORRECT ANSWER-Primary organs
ex. bone marrow, thymus
Where do mature lymphocytes interact with antigen? - CORRECT ANSWER-
Secondary organs
What are the three signals required for T cell activation? - CORRECT ANSWER-1.
TCR signaling
2. Costimulatory interaction
3. Cytokine signaling (ex. autocrine and paracrine IL-2)
What cytokine is important for T cell activation? - CORRECT ANSWER-IL-2
Why are alpha beta T cells CD3+ and gamma delta T cells CD3-? - CORRECT
ANSWER-CD3 is responsible for antigen-MHC T cell activation and gamma delta T
cells do not require the MHC for T cell activation
What is the Src family? - CORRECT ANSWER-A family of tyrosine kinases that
contains 6 conserved domains, including SH2 and SH3. Src family kinases play a
role during T cell activation
Describe the first phase of T cell activation - CORRECT ANSWER-1. TCR engages
with MHCII (or MHCI)
2. CD4 (or CD8) stabilizes the interaction
3. CD45 activates Lck on CD4 (or CD8)
4. Lck phosphorylates ITAMs found on CD3 (gamma, delta, epsilon, zeta chains)
5. ZAP-70 uses SH2 domain to dock to ITAMs
6. ZAP-70 phosphorylates LAT (linker protein of activated T cells) and SLP-76
Describe positive selection - CORRECT ANSWER-MHC is presented to naive T
cells. T cells which bind well to MHC are positively selected for. If there is weak
binding, the cell undergoes apoptosis (programmed cell death). If the cell binds
strongly to MHCII, the cell upregulates ThPOK and downregulates Runx3 to
become a CD4+ T cell. Otherwise, the cell becomes a CD8+ T cell
ThPOK+Runx3- - CORRECT ANSWER-CD4+ T cell
ThPOK-Runx3+ - CORRECT ANSWER-CD8+ T cell
Describe negative selection - CORRECT ANSWER-If a T cell binds too strongly to
MHC, the cell undergoes apoptosis
Why is negative selection important? - CORRECT ANSWER-It is a measure to
protect against autoimmunity
, How does negative selection ensure T cells don't respond inappropriately to
peptide-MHC complexes not found in the thymus? - CORRECT ANSWER-AIRE is
a protein that induces expression of proteins not found in the thymus, ex. lung
protein, to ensure that T cells do not react to proteins found throughout the body
after undergoing negative selection
How do T cells move through the thymus? - CORRECT ANSWER-1. Arrive to
thymus via corticomedullary junction
2. Differentiate into T cells in thymic epithelium
3. Move into thymic cortex where they proliferate and express TCR
4. Selection process
5. Move to thymic medulla
6. Leave via corticomedullary junction
What is the role of Bcl-2? - CORRECT ANSWER-Prevents apoptosis by inhibiting
Bax and Bak
What is the function of Bax and Bak? - CORRECT ANSWER-Open mitochondrial
membrane, releasing cytochrome C, triggering apoptosis
What is the function of Fas? - CORRECT ANSWER-Induces apoptosis
How does the signal from an antigen influence T cell survival? - CORRECT
ANSWER-Antigen signal prevents apoptosis by upregulating Bcl-2, without a
signal from antigen, T cells downregulate Bcl-2, leading to apoptosis as a
protection measure against autoimmunity
What ligand determines whether bone marrow stem cells will differentiated in B
cells or T cells? - CORRECT ANSWER-Notch, Notch positive cells become T cells
while Notch negative cells become B cells
Bone marrow stem cells exposed to Notch will become - CORRECT ANSWER-T
cells
Where are Notch ligands found? - CORRECT ANSWER-The thymic epithelium
Which process is responsible for driving CD4 or CD8 expression? - CORRECT
ANSWER-Positive selection
Where do lymphocytes reach maturity? - CORRECT ANSWER-Primary organs
ex. bone marrow, thymus
Where do mature lymphocytes interact with antigen? - CORRECT ANSWER-
Secondary organs
