BHS 316 Quiz 6
In the thymus, T cells undergo tests for which of the following concepts: (check all that apply)
If they recognize self-peptides presented on MHC molecules If they recognize self-MHC molecules
Testing for tolerance of self is also known as:
Negative selection
A double positive T cell in the thymus that has [ Select ] levels of Fas on its surface and [ Select ] levels of Bcl-2 on its surface is [ Select ] to cellular signals that can lead to apoptosis.
Answer 1: High Answer 2: Low Answer 3: Very sensitive
The cytokine that blocks the co-stimulatory signals such as expression of the CD28 receptor, and therefore reduces the ability of APCs to activate a T cell is [ Select ]. The cytokine that reduces the proliferation rate of T cells and makes cytotoxic T cells less effective at killing cells is [ Select ].
Answer 1: IL-10 Answer 2: TGFb
Naïve T cells are [ Select ], which is necessary for these cells to [ Select ]. T cells that have already proliferated are [ Select ], which is necessary for these cells to [ Select ].
Answer 1: Long-lived Answer 2: Recirculate looking for their cognate antigen Answer 3: Short-lived Answer 4: Not fill our bodies with weapons from old invasions
When the B7 protein on the surface of APCs binds to CD28 on a virgin T cell, the signal transmitted to the T cell is [ Select ]. When the same B7 protein on the surface of APCs binds to CTLA-4 on an experienced T cell, the signal transmitted to the T cell is [ Select ].
Answer 1: Become activated Answer 2: Become deactivated
The B7 protein binds to [ Select ] with much higher affinity than it binds to [ Select ] making it [ Select ] that T cells will be continually reactivated.
Answer 1: CTLA-4 Answer 2: CD28 Answer 3: Less likely
Proteins found in many of our tissues are called [ Select ]. Proteins found only in the liver (for example) or only in the heart are called [ Select ]. In order to ensure that T cells trained in the thymus that will later move throughout the body are tolerant of the kinds of proteins they could find anywhere in the body, [ Select ] cells in the thymus express proteins [ Select ].
Answer 1: Shared proteins Answer 2: Tissue-specific proteins Answer 3: Medullary thymic epithelial Answer 4: That would usually be expressed in other tissues
T cells are educated to tolerate self in the [ Select ], and B cells are educated to tolerate self in the [ Select ].
Answer 1: Thymus Answer 2: Bone marrow
The immune system cells that can protect against T cells that may react to self antigen are called [ Select ] , and the immune system cells that keep T cells from overreacting to truly foreign antigens are called [ Select ].
Answer 1: nTregs Answer 2: iTregs
NK cells that lack inhibitory molecules consistent with that person's class I MHC molecules:
Are killed to avoid instigating an autoimmune response
The most accurate description of how T cells and B cells recognize antigen is that:
B cells should be to recognize antigen that is presented by MHC molecules and antigen that is not presented by MHC molecules, but T cells should only recognize antigen that is presented by MHC molecules
Which of the following is correct? CD4 co-receptors bind to class II MHC molecules and CD 8 co-receptors bind to class I MHC molecules CD4 co-receptors bind to class I MHC molecules and CD 8 co-receptors bind to class II MHC molecules CD4 and CD 8 co-receptors bind to class I MHC molecules CD4 and CD 8 co-receptors bind to class II MHC molecules
CD4 co-receptors bind to class II MHC molecules and CD 8 co-receptors bind to class I MHC molecules
A "nude" T cell is one that does not have (check all that apply):
CD8 TCR CD4
The cytokines produced by Tregs include:
IL-10 and TGFb
T cells that react to very rare self antigen may not be selected against because they may never "meet" their cognate antigen during the negative selection part of education. It is likely that:
If the self antigen to which a T cell reacts is so rare as to not be encountered by a T cell during education, then that same self antigen is unlikely to be encountered by the T cell once it graduates.
T cells exhibit the Fas protein on their surface. When this protein binds to Fas ligand, or FasL, the result is:
Death of the T cell
Put the following events in deactivation of the immune system in order from the beginning:
First Invaders are killed during the immune response, decreasing the number of invaders present Second Fewer innate system immune cells are activated at the battle site Third Fewer dendritic cells are activated Fourth Fewer dendritic cells mature Fifth Fewer dendritic cells travel to the secondary lymphoid organs to inform the immune system about the invader
Put the following events in of T cell education in the thymus in order from the beginning:
First event Naïve T cells migrate to the thymus Second event T cells rearrange gene segments for the a and b chains of the TCR Third event T cells begin to express low levels of TCR Fourth event T cells produce a TCR and CD4, and CD8 molecules, which are translocated to the surface of the cell Fifth event Double positive cells contain high levels of Fas antigen and low levels of Bcl-2
In the thymus, T cells go through positive and negative selection to be "educated". When they "graduate", the result is T cells that:
Have TCRs which do not recognize self-peptides presented on MHC molecules but which do recognize self MHC-peptide complexes
One way your body ensures that immune cells built to fight an invader to do not continue to wage war after a pathogen has been eliminated is to:
Make the immune cells short-lived
The concept that the need for co-stimulation of T cells protects us from virgin T cells that "wander" (unauthorized) into tissues is called:
Peripheral tolerance
MHC restriction is also known as:
Positive Selection
Cortical thymic epithelial cells can display which of the following: (check all that apply)
Proteins made inside the cell via class I MHC molecules Proteins made inside the cell via class II MHC molecules Proteins made outside the cell via class II MHC molecules
Virgin B cells that don't pass the first test of having produced antibodies that do not react to self are given a second chance to change their light chain genes to create a new receptor in a process called:
Receptor editing
T cells whose job is to downregulate the immune system are called:
Regulatory T cells
Virgin T cells are not allowed to travel to tissues, but are allowed to travel to secondary lymphoid organs. This traffic pattern is:
Related to tolerance because the secondary lymphoid tissues will have self antigen very similar to the thymus, and virgin T cells that would have reacted to these self antigens should have been eliminated during education.
The broad concept of by which our B and T cells "learn" to not react to our own bodies is called:
Self-tolerance
Dendritic cells can determine what type of invader is present by: (check all that apply)
Sensing the cytokines present in tissues Identifying general classes of invaders via their Toll-like receptors
Once a dendritic cell has identified an invader, what mechanism(s) does it use to pass that information on to helper T cells? (check all that apply)
Specific co-stimulatory molecules on the DC's cell surface Production of specific cytokines
The PD-1L protein on the surface of a T cell increases after activation, and when it binds to the PD-1 protein, that binding:
Stops T cells from proliferating
Naïve T cells can be induced to become regulatory T cells through exposure to:
TGFb
To pass the MHC restriction test, T cells must recognize MHC plus self peptide, but to pass the tolerance test, T cells must *not* recognize MHC plus self peptide. How can one T cell satisfy both tests? Features that might allow this to happen include: (check all that apply)
That the T cell may react differently to the specific kinds of cells that ask the exam questions That the internal cellular circuitry of T cell itself may change as the T cell passes from one exam to the next
A single positive T cell means that:
The T cell expresses only one of CD4 or CD8
T regs are important in preventing: (check all that apply)
mast cell degranualtion our intestines from overreacting to harmless resident bacteria the overreaction of the immune system that we call allergies
The best explanation of T cell education is:
The vast majority of T cells your body makes fail at least one of the two tests in the thymus and then die by apoptosis in the thymus
If a virgin T cell that recognizes self-antigen accidentally "slips" through education process in the thymus and that cell slips through passport-control and into tissues, its TCR may find its cognate antigen on a heart cell (for example). If this happens, then the most likely result is that:
The virgin T cell would not become activated because the co-stimulation required by an APC (or B cell) would not occur when binding to antigen on the heart cell.
Graduated T cells express: (check all that apply)
Their TCR and one of either CD4 and CD8 co-receptors, but not both
If an NK cell comes upon another cell in your body that produced no class I MHC molecules, it will kill that cell because of the principle called:
missing self recognition
During positive selection, double positive T cells that do not recognize the complex of self MHC molecules and their presented peptide have what fate?
They die
Virgin B cells that produce BCRs that recognize self antigen largely have what fate?:
They die in the bone marrow
T cells are born in the bone marrow and are taught self tolerance initially when they leave the bone marrow and move to the:
Thymus
Even if a self-reactive virgin T cell was able to move into tissue and found its cognate antigen at high enough concentrations to be activated, the continued activation would result in:
Tolerance due to AICD
Select all types of cells that go through some level of "tolerance" training: (check all that apply)
Virgin T cells Virgin NK cells Virgin B cells
Negative selection is about keeping T cells that recognize:
foreign peptides as opposed to self peptides
Abnormal MHC presentation in the cortical thymic epithelial cells that results from autophagy occurs when proteins made:
inside the cell are displayed via class II MHC molecules
Positive selection is about keeping T cells that recognize:
presented antigen as opposed to unpresented antigen
Negative selection works to eliminate T cells:
with TCRs that recognize self antigen presented on MHC molecules
Positive selection works to eliminate T cells:
with TCRs that recognize unpresented antigen
If a Virgin B cell "breaks the rules" and moves into tissues and finds its cognate antigen, it will most likely:
would not become activated because the co-stimulation required by a helper T would not be likely to occur.
