Immunology Midterm 2

Non-traditional T cells:

- Are most abundant in areas that are in contact with the external environment. -Do not express CD4 or CD8 co-receptors

Testing for tolerance of self is also known as:

negative selection

Experienced T cells have license to visit:

Secondary lymphoid organs similar to those where they gained experienced

The kinds of B cells that typically undergo somatic hypermutation and/or class switching are (check all that apply):

B cells that have been activated through T cell-dependent activation

IgE antibodies

-Defend against parasites -Cause degranulation of mast cells -Are produced upon exposure to an antigen -Cause allergies

Graduated T cells express:

Their TCR and one of either CD4 and CD8 co-receptors, but not both

IgG antibodies:

-Are effective at neutralizing viruses -Help NK cells kill more effectively via ADCC -Are effective at opsonizing invaders for phagocytosis -Are somewhat effective at fixing complement -Contain 2 Fab regions -Can pass from the mother to a developing fetus in utero -Have several different variants of their Fc regions, which allow subclasses to have different functions -Are in gamma globulin shots -Are the longest-lived antibody class

IgA antibodies

-Are unable to fix complement -Coat pathogens so they can be transported out of the body with feces -Ace resistant to acids and proteolytic enzymes in the digestive tract -Can prevent invaders from attaching to intestinal epithelium -Defend mucosal surfaces -Contain 4 Fab regions -Most abundant antibody in the human body

TCRs from traditional T cells and BCRs are the same in which of the following ways (check all that apply):

-Both have extracellular and intracellular components that allow recognition of an antigen and transmission of a signal inside the cell. -The variation in receptors between different T cells are the result of a mix-and-match strategy that uses the RAG proteins.

Dendritic cells can become activated by:

-Compounds secreted by cells being killed by a pathogen -TNF secreted by macrophages and neutrophils -Pattern-recognition receptors that are on the surface of dendritic cells that recognize a pathogen directly

IgM antibodies

-Contain 10 Fab regions -Are the first class of antibodies made upon activation of naïve B cells -Are highly efficient at fixing complement -Are efficient at neutralizing viruses -Were the first class of antibody to evolve -Are the largest of the antibodies

NKT cells:

-Have limited diversity of TCRs -Recognize lipid antigens -Have some properties of traditional T cells and some properties of NK cells

Dendritic cells are _________ and plasmocytoid dendritic cells are ___________ .

-cells that present antigens -Cells that produce IFNa and IFNb in response to viral attack

The purpose of activated macrophages presenting antigens is to _________________, and the purpose of activated dendritic cells presenting antigens is to ___________________ .

-continually stimulate experienced T cells so that they stay activated -activate virgin T cells so they can contribute to the battle against invaders

Put the following events in the activation of a helper T cell in order from beginning to end:

1. A T cell binds to the cognate antigen being presented by a class II MHC molecule 2. The T cell's CD4 co-receptors clip into the class II MHC molecule of the APC, stabilizing the interaction between the T cell and APC. 3. The expression of adhesion molecules on the surface of the T cell is upregulated. 4. The expression of CD40L on the surface of the T cell are upregulated, increasing the ability to bind to the APC's CD40 proteins, which results in production of co-stimulatory molecules like B7 on the surface of the APC. 5. The T cell and APC separate. 6. The Th cells proliferate

Class II MHC molecules are specifically useful for antigen presentation because they:

1. Are able to describe pathogens in the extracellular environment (i.e., blood, tissues) 2. Ensure that activation of the adaptive immune system occurs when both an APC and T cell agree that a potentially dangerous invasion has occurred 3. Ensure that smaller epitopes are available for "viewing" as opposed to large, folded proteins

Antigen ends up in a lymph node through what mechanisms?

1. By being attached to antibodies or complement that enter via lymph 2. By being carried by an APC into the lymph nodes

When a TCR-peptide-MHC complex forms, the upregulation of CD 40L on the surface of the helper T cell:

1. Causes the APC to produce more CD40 proteins on its surface 2. Causes the T cell to be more able to activate B cells 3. Improves the lifespan of the APC

Both CTLs and NK cells can kill infected cells using which mechanisms:

1. FasL 2. Perforin/Granzyme

When a dendritic cell senses a virus or bacteria that infects your cells, it will travel to nearby lymph nodes and produce _____________ . If the dendritic cell can find a Th cell that binds to the DC's MHC-antigen complex, the Th cell will become a _____________ cell and will produce _____________ . These cytokines result in _____________ .

1. IL-12 2. Th1 3. IL-2, TNF, and IFN-g 4. Activation of macrophages and NK cells and production of IgG antibodies

When a dendritic cell senses a parasite or pathogenic bacteria in your intestines, it will travel to nearby lymph nodes. If the dendritic cell can find a Th cell that binds to the DC's MHC-antigen complex and the _____________ cytokine is present, the Th cell will become a _____________ cell and will produce _____________ . These cytokines result in _____________ .

1. IL-4 2. Th2 3. IL-4, IL-5, and IL-13 4. Production of IL-4, IgA and IgE antibodies, and mucus

Dendritic cells can determine what type of invader is present by:

1. Identifying general classes of invaders via their Toll-like receptors 2. Sensing the cytokines present in tissues

In the thymus, T cells undergo tests for which of the following concepts:

1. If they recognize self-MHC molecules 2. If they recognize self-peptides presented on MHC molecules

Put the following events in deactivation of the immune system in order from the beginning:

1. Invaders are killed during the immune response, decreasing the number of invaders present 2. Fewer innate system immune cells are activated at the battle site 3. Fewer dendritic cells are activated 4. Fewer dendritic cells mature 5. 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:

1. Naïve T cells migrate to the thymus 2. T cells rearrange gene segments for the a and b chains of the TCR 3. T cells begin to express low levels of TCR 4. T cells produce a TCR and CD4, and CD8 molecules, which are translocated to the surface of the cell 5. Double positive cells contain high levels of Fas antigen and low levels of Bcl-2

Class I MHC molecules are specifically useful for antigen presentation because they:

1. Prevent cytotoxic T cells from killing cells that are surrounded by pathogenic debris outside the cell. 2. Ensure that activation of the adaptive immune system occurs when both an APC and T cell agree that a potentially dangerous invasion has occurred. 3. Allow cytotoxic T cells to focus on cells that have been infected 4. Allow cytotoxic T cells to "see" proteins that are made inside an infected cell that would otherwise not be visible to the immune system. 5. Ensure that smaller epitopes are available for "viewing" as opposed to large, folded proteins

Cortical thymic epithelial cells can display:

1. Proteins made inside the cell via class II MHC molecules 2. Proteins made outside the cell via class II MHC molecules 3. Proteins made inside the cell via class I MHC molecules

Once a dendritic cell has identified an invader, what mechanism(s) does it use to pass that information on to helper T cells?

1. Specific co-stimulatory molecules on the DC's cell surface 2. Production of specific cytokines

When a dendritic cell senses a fungus or extracellular bacteria in your tissues, it will travel to nearby lymph nodes and produce ___________. If the dendritic cell can find a Th cell that binds to the DC's MHC-antigen complex, the Th cell will become a _____________ cell and will produce _____________ . These cytokines result in _______________.

1. TGFb and IL-6 2. Th17 3. IL-17 and IL-21 4. Recruitment of neutrophils and production of antibodies that can opsonize fungi and bacteria

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:

1. That the internal cellular circuitry of T cell itself may change as the T cell passes from one exam to the next 2. That the T cell may react differently to the specific kinds of cells that ask the exam questions

Which of the following are features of apoptosis of an infected cell?

1. The genetic material of viruses that have infected the cell is destroyed 2. Cellular debris from the dead cell is packaged in vesicles

Proteins found in many of our tissues are called ___________. Proteins found only in the liver (for example) or only in the heart are called ___________ . 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,___________] cells in the thymus express proteins ___________ .

1. shared proteins 2. tissue-specific proteins 3. medullary thymic epithelial 4. that would usually be expressed in other tissues

T regs are important in preventing:

1.the overreaction of the immune system that we call allergies 2. our intestines from overreacting to harmless resident bacteria 3. mast cell degranualtion

Clonal selection can best be described as:

Activated helper T cells producing factors that upregulate their growth to focus proliferation on T cells that have recognized invaders

Delayed-type hypersensitivity is the result of:

Both a specific and a non-specific immune response

Activated T cells have license to visit:

Both secondary lymphoid organs and sites of inflammation

The protein molecules that display (i.e., present) lipids instead of the classical peptides are called:

CD1 proteins

helper T cells use ________ as the co-receptor.

CD4

A "nude" T cell is one that does not have:

CD4 CD8 A TCR

CTLs use __________ as the co-receptor.

CD8

The B7 protein binds to _______ with much higher affinity than it binds to ________, making it ________that T cells will be continually reactivated.

CTLA-4 CD28 less likely

Follicular dendritic cells use what molecule to attract B cells so the B cells may "sample" their antigens?

CXCL13

HLA-DM does what

Competes with other peptides for binding to class II MHC molecules

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____________ The cytokine that reduces the proliferation rate of T cells and makes cytotoxic T cells less effective at killing cells is ___________.

IL-10 TGFb

The cytokines produced by Tregs include:

IL-10 and TGFb

Peptides fragments in the cytoplasm of human cells are taken to the endoplasmic reticulum by:

TAP transporters

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/F Most mature T cells circulating in the body have gd receptors on their surface.

F

The portion of the antibody that changes during somatic hypermutation is the ______ , and the portion of the antibody that changes during class switching is the ________ .

Fab region Fc region

The secondary lymphoid structure with the job of presenting opsonized antigens to B cells is:

Follicular dendritic cells

A class I MHC molecule is made up of:

HLA protein B2-microglobulin

What kind of cell serves as the mechanism for getting antigen into the Peyer's patch?

M cell

Antigens that are transported from the MALT to Peyer's patches are:

Only antigens that can bind to the surface of an M cell

The lymph nodes main purpose is to:

Organize and concentrate antigen presentation to increase the chance of lymphocytes finding their cognate antigen

A primary lymphoid follicle becomes a secondary lymphoid follicle by:

Presenting opsonized antigen to B cells and cross-linking their BCRs, resulting in B cell proliferation

T/F CD4 co-receptors bind to class II MHC molecules and CD 8 co-receptors bind to class I MHC molecules

T

____________ can only recognize their cognate antigens if they are presented, but ____________ cells can recognize their cognate antigens if they are not presented (i.e., soluble).

T cells B cells

Which types of cells can go through repeated cycles of activation, proliferation, recirculation, and re-stimulation?

T cells and B cells

The cellular component that screens for peptide fragments that have approximately the correct number of amino acids and the right kind of amino acids on their ends for presentation on a class I MHC molecule is:

TAP transporters

In traditional T cells, the TCR signaling requires that:

TCRs cluster near each other on the surface of a T cell

Naïve T cells can be induced to become regulatory T cells through exposure to:

TGFb

IL-12 is a cytokine that causes uncommitted T helper cells to become what class of T helper cell?

Th1

The three broad profiles, or subsets, of groups of cytokines are:

Th1, Th2, Th17

IL-6 and TGFb are cytokines that cause uncommitted T helper cells to become what class of T helper cell?

Th17

IL-4 is a cytokine that causes uncommitted T helper cells to become what class of T helper cell?

Th2

In the Peyer's patch, the Th cells secrete what kind of cytokine profile?

Th2

A single positive T cell means that:

The T cell expresses only one of CD4 or CD8

The structures which can best be described as a sea of B cells that contain islands of follicular dendritic cells are called

lymphoid follicles

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

In order for an activated B cell in a germinal center to engage in somatic hypermutation on class switching, activated B cells interaction between:

Their CD40 protein and the CD40L receptor on the surface of Tfh cells

Activated T cells can identify the B cells that they can help because the T cells recognize:

Their cognate antigen that is expressed on class II MHC molecules on the surface of B cells

The immune system cells that can protect against T cells that may react to self antigen are called _________ , and the immune system cells that keep T cells from overreacting to truly foreign antigens are called _________.

nTregs iTregs

Which of the following processes occur often in germinal centers? a. Phagocytosis of dead B cells b. B cell proliferation c. Maturation of T cells d. Somatic hypermutation e. Phagocytosis of the invader f. Co-stimulation of B cells by helper T cells g. Follicular dendritic cells displaying opsonized antigen h. Neutrophils killing invaders directly i. Complement production j. Class switching

a. Phagocytosis of dead B cells b. B cell proliferation d. Somatic hypermutation f. Co-stimulation of B cells by helper T cells g. Follicular dendritic cells displaying opsonized antigen j. Class switching

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 ___________. 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 ___________.

activated deactivated

Activated T cells have license to visit specific areas of the body, and their ability to visit a site (or to not visit a site) is controlled by:

adhesion molecules

The "passport" that Virgin T cells have that allow them to visit specific sites in the body are:

adhesion molecules

Virgin T cells have permission to visit:

all secondary lymphoid organs

NK cells that lack inhibitory molecules consistent with that person's class I MHC molecules:

are killed to avoid instigating an autoimmune disease

Which of the following are primary lymphoid organs? a. Mucosal-associated lymphoid tissue b. Thymus c. Lymph nodes d. Bone marrow e. Spleen

b and d

Both B and T cells begin life in the:

bone marrow

To be activated, a naïve helper T cell requires formation of the TCR-antigen-MHC complex and:

co-stimulation by the APC displaying the antigen

What kinds of cells inspect the peptides presented on class I MHC molecules?

cytoxic T cells

Class I MHC molecules present to ________ and class II MHC molecules present to________

cytoxic T cells helper T cells

Negative selection is about keeping T cells that recognize:

foreign peptides as opposed to self peptides

A double positive T cell in the thymus that has ___________ levels of Fas on its surface and [ Select ] levels of Bcl-2 on its surface is _____________ to cellular signals that can lead to apoptosis.

high low very sensitive

The structure through which B and T cells are able to enter secondary lymphoid organs, such as lymph nodes, is called the:

high endothelial venule

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

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

Proteins that have many different variants across the human population are called:

polymorphic

MHC restriction is also known as:

positive selection

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

The "typical" job of proteasomes in an uninfected human cell is:

recycle defective proteins

The phenomenon in which high levels of rates of change occur in the DNA encoding V, D, and J gene segments is called:

somatic hypermutation

Peyer's Patches are located in what tissue:

spleen, lymph nodes, MALT

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 cells from proliferating

Positive selection works to eliminate T cells:

that recognize unpresented antigen

Virgin B cells that produce BCRs that recognize self antigen largely have what fate?

they die in the bone marrow

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:

virgin NK cells virgin B cells virgin T cells

B cells that have encountered their cognate antigen on a follicular dendritic cell in a lymph node upregulate the expression of the receptor CCR7 because that receptor recognizes a chemokine that is produced:

where Th cells and B cells meet so B cells can be activated