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.