PCB 4233 Immunology Exam Study Questions
and Correct Answers-
What are double negative; double positive T cells? - ✔✔Double negative cells don't
express CD4- or CD8- thus they are known as double negative. Double positive express
both CD4+ and CD8+ thus are known as double positive
At what stage is the pre-TCR expressed? - ✔✔DN stage 2 lymphoid precursor
expresses pre-T cell and can no longer differentiate into NK cell or B cell. Receptor
known as notch on thymic endothelial cells commits them to T cell lineage
Signaling of the pre-TCR occurs as a result of successful assembly of the pre-TCR. How
does this vary from signaling during positive and negative selection? - ✔✔Positive
selection selects thymocytes bearing receptors capable of binding self-MHC molecules,
resulting in MHC restriction
Negative selection selects thymocytes bearing high-affinity receptors for self-
MHC/peptide complexes, resulting in self tolerance
What events follow successful signaling through the pre-TCR? - ✔✔Thymocytes enter
DP stage of selection, functional TCR⍺ chain replaces surrogate pre-TCR⍺, pos/neg
selection occurs yielding mature SP T cell, cessation of proliferation
Injecting a TCR transgenic mouse with the peptide it recognizes, in its thymus, would
result in an increase in which process? - ✔✔Negative selection
During positive selection what happens and what type of signal induces cell death?
(Strong, intermediate, no signal, intermittent?) - ✔✔When TCR's don't bind the cells
die from neglect (this occurs most frequently), when TCRs bind too strongly the cells are
deleted via negative selection, when TCRs bing intermediately the cells go on to positive
selection, these cells that can bind MCH go on to become SP CD4+ or CD8+ cells
, During negative selection what happens and what type of signal induces cell death? -
✔✔A strong signal induces cell death, apoptosis is induced if cells with too strong
anti-self signaling/binding
Ultimately some autoreactive cells escape negative selection in the thymus. Describe
what happens to these cells? - ✔✔They attack self tissue, they can be rendered
anergic, they negatively regulate other autoreactive cells, and they require TCR ligation
and costimulation to become activated
What is T cell anergy? - ✔✔T cell anergy occurs when autoreactive T cells are not
deleted via apoptosis and instead become inactivated, preventing them from becoming
effector T cells
What two signals are required to elicit an immune response? - ✔✔Peptide-MHC and
co-stimulation via B7 are two stimuli needed to activate an immune response
Describe peripheral tolerance - ✔✔Peripheral tolerance is a mechanism the immune
system utilizes to ensure autoreactive T cells do not attack self-tissue
What is AIRE, where is it expressed and how is it involved in T cell development? -
✔✔AIRE (transcription factor located in medulla of thymus), alternate means of
negative selection, autoimmune regulator protein. It exposes maturing T cells to
proteins from tissue specific cells throughout the body, T cells that react to the proteins
are destroyed. Medullary region is important in removing autoreactive T cells
What are superantigens and how do they differ from regular peptide antigens? -
✔✔class of antigens that cause non-specific activation of T-cells resulting in
polyclonal T cell activation and massive cytokine release
and Correct Answers-
What are double negative; double positive T cells? - ✔✔Double negative cells don't
express CD4- or CD8- thus they are known as double negative. Double positive express
both CD4+ and CD8+ thus are known as double positive
At what stage is the pre-TCR expressed? - ✔✔DN stage 2 lymphoid precursor
expresses pre-T cell and can no longer differentiate into NK cell or B cell. Receptor
known as notch on thymic endothelial cells commits them to T cell lineage
Signaling of the pre-TCR occurs as a result of successful assembly of the pre-TCR. How
does this vary from signaling during positive and negative selection? - ✔✔Positive
selection selects thymocytes bearing receptors capable of binding self-MHC molecules,
resulting in MHC restriction
Negative selection selects thymocytes bearing high-affinity receptors for self-
MHC/peptide complexes, resulting in self tolerance
What events follow successful signaling through the pre-TCR? - ✔✔Thymocytes enter
DP stage of selection, functional TCR⍺ chain replaces surrogate pre-TCR⍺, pos/neg
selection occurs yielding mature SP T cell, cessation of proliferation
Injecting a TCR transgenic mouse with the peptide it recognizes, in its thymus, would
result in an increase in which process? - ✔✔Negative selection
During positive selection what happens and what type of signal induces cell death?
(Strong, intermediate, no signal, intermittent?) - ✔✔When TCR's don't bind the cells
die from neglect (this occurs most frequently), when TCRs bind too strongly the cells are
deleted via negative selection, when TCRs bing intermediately the cells go on to positive
selection, these cells that can bind MCH go on to become SP CD4+ or CD8+ cells
, During negative selection what happens and what type of signal induces cell death? -
✔✔A strong signal induces cell death, apoptosis is induced if cells with too strong
anti-self signaling/binding
Ultimately some autoreactive cells escape negative selection in the thymus. Describe
what happens to these cells? - ✔✔They attack self tissue, they can be rendered
anergic, they negatively regulate other autoreactive cells, and they require TCR ligation
and costimulation to become activated
What is T cell anergy? - ✔✔T cell anergy occurs when autoreactive T cells are not
deleted via apoptosis and instead become inactivated, preventing them from becoming
effector T cells
What two signals are required to elicit an immune response? - ✔✔Peptide-MHC and
co-stimulation via B7 are two stimuli needed to activate an immune response
Describe peripheral tolerance - ✔✔Peripheral tolerance is a mechanism the immune
system utilizes to ensure autoreactive T cells do not attack self-tissue
What is AIRE, where is it expressed and how is it involved in T cell development? -
✔✔AIRE (transcription factor located in medulla of thymus), alternate means of
negative selection, autoimmune regulator protein. It exposes maturing T cells to
proteins from tissue specific cells throughout the body, T cells that react to the proteins
are destroyed. Medullary region is important in removing autoreactive T cells
What are superantigens and how do they differ from regular peptide antigens? -
✔✔class of antigens that cause non-specific activation of T-cells resulting in
polyclonal T cell activation and massive cytokine release
