FINAL MICRB 410 (all practice questions)

Purified naive T cells isolated from a T-cell receptor transgenic mouse represent a homogeneous population of cells with specificity for a single known peptide:MHC complex. This specific peptide:MHC complex can be purified and formed into multivalent complexes, such as peptide:MHC tetramers. When the naive T cells are stimulated with their 'antigen' in the form of these peptide:MHC tetramers, the T cells show activation responses, including the up-regulation of genes that are induced within several hours after T-cell receptor stimulation. However, these activated T cells fail to undergo robust proliferation, and the majority of cells die after 3-4 days in culture. T cell proliferation and survival could be greatly augmented by addition of:

B7 ligands for CD28

Which of the following mechanisms of mutagenesis mediated by AID activity is possible? Select all that apply.

Base excision repair, followed by error-prone DNA polymerase fill-in of the gap created. Mismatch repair, followed by error-prone DNA polymerase fill-in of the gap created. The lesion is not repaired prior to replication, resulting in a CG→TA transition.

Which of the following statements is TRUE about B-1 B cells and MZB cells? Select all that apply.

Both are self-renewing in the periphery, not requiring replacement from bone marrow. Both can respond to TI antigens Both predominantly produce IgM

Which of the following occurs when macrophages become activated after phagocytosing a pathogen? 1. Presentation of peptides from the pathogen on MHC class I molecules 2. Secretion of inflammatory mediators to recruit and activate T cells and neutrophils 3. Direct activation of B cells by macrophages 4. An increase in co-stimulatory molecules for interacting with T cells

2 and 4 only

CXCR5 is the receptor for the chemokine CXCL13, secreted by follicular stromal cells and follicular dendritic cells in the B cell zones (i.e., lymphoid follicles) of secondary lymphoid organs. A conditional knockout mouse in which CXCR5 was specifically deleted only in T cells would have ___

A defect in T cell-dependent antibody responses

A T cell line growing in culture is subjected to a chemical mutagen, and individual mutant lines are derived from this population. The individual mutant cell lines are each screened for their ability to proliferate in response to stimulation with antibodies to the T-cell receptor plus CD28 (anti-CD3 + anti-CD28). In addition, the cells are treated with varying doses of added IL-2, and three days later, T cell proliferation is measured by 3H-thymidine incorporation (cpm). The data for one mutant line and the wild-type control are shown in the figure below. Based on the data, the gene that is defective in this mutant T cell line most likely encodes _____________________.

CD25, also known as the IL-2 receptor alpha chain

At least some NK-T cells (NKTs) express ________

CD4

Individuals with the HIV-induced immunodeficiency disease AIDS have a progressive loss in the number of CD4 T cells in their bodies. These patients have a greatly increased rate of life-threatening disease caused by the inability of their immune system to control infections of the intracellular bacterium, Mycobacterium tuberculosis (Mtb). Mtb infects macrophages and then replicates in the cell's phagosomes. The most important immune mechanism lacking in these patients that leads to their increased susceptibility to Mtb is a defect in:

CD4 T cell help for cytotoxic effector CD8 T cells

B cells follow which of the following chemotactic signals to migrate to the cortical regions of secondary lymphoid tissue?

CXCL13

Which of the following antigen types could be characterized as TI antigens?

Capsular polysaccharides Bacterial cell wall components

Studies show that about 50-100 different B cells initially seed each germinal center (d7 post-infection). These different B cells are represented by different colored circles in a white oval (germinal center) in the figure below. Which of the choices shown best represents the B cell population that would be found in the same germinal center approximately two weeks later? INSERT PICTURE HERE

D (all teal blue)

Which of the following do you expect would be actively functioning in a B cell that had migrated to a germinal center?

AID

Which of the following statements about NK-T cells is TRUE?

Activated NK-T cells can act as both TH and TC cells.

Cross-regulation of various members of a subset of T cells is frequently observed with:

All TH cells

You isolate naïve T cells from your own blood and want to polarize them to the TH1 lineage. You can use any of the following reagents to do this. Which would you choose?

Anti-TCR antibody IL-12 Anti-CD28 antibody

The vaccine to Haemophilus influenzae type b is called a conjugate vaccine. It is composed of the tetanus toxoid protein conjugated to the capsular polysaccharide of the H. influenzae type b bacteria. When used to vaccinate infants, the antibody response generated by this vaccine would include:

Antibodies to the bacterial polysaccharide and the tetanus toxoid

In germinal centers, proliferating B cells undergo a process called somatic hypermutation, in which mutations are introduced into the V regions of the antibody heavy and light chain genes. When this process is complete after several weeks, the overall affinities of the antibodies produced are greatly increased compared to those present early in the primary response. The somatic hypermutation process leads to increased antibody affinity because:

B cells making higher affinity antibodies receive more help from TFH cells.

Borrelia hermsii is a spirochete bacterium, transmitted by tick bites, that causes an illness characterized by a relapsing fever. The bacteria enter the host bloodstream and replicate there. Studies in mice show that episodes of bacteremia (bacteria in the blood) are efficiently controlled by anti-bacterial antibodies, but interestingly, follicular B cells are not required for this response, nor is the response impaired by splenectomizing the mice (i.e., removing the spleen). Which B cells are most likely responsible for this antibody response?

B-1 B cells

The kinetics of a typical CD8 T cell response to an acute virus infection in mice is shown in the figure below. In this example, the virus is cleared by ~day 7 post-infection, and starting at ~day 10 post-infection, the majority of the virus-specific CD8 T cells die. The death of these virus-specific CD8 T cells is caused by:

Fas-induced death or cytokine withdrawal NOTE: Yes. When an infection is effectively repelled by the adaptive immune system, most effector T cells undergo 'death by neglect,' removing themselves by apoptosis. The resulting 'clonal contraction' of effector T cells appears to be due both to the loss of pro-survival cytokines that are produced by antigenic stimulation, such as IL-2, and to the loss of expression of receptors for these cytokines. While many effector T cells die from the loss of survival signals and the activation of the Bim-mediated intrinsic pathway of apoptosis, effector T cell death can also occur via the extrinsic pathway of apoptosis that is activated by signaling via members of the TNF receptor superfamily, particularly Fas (CD95).

Effector caspases are activated downstream of both extrinsic and intrinsic pathways of apoptosis. Consequently, cells lacking one or more of these enzymes show defects in apoptosis. An alternative means of eliminating the activity of an effector caspase would be to:

Generate a form of the pro-caspase with a mutation in the initiator caspase cleavage site. NOTE: Yes. If this cleavage site is mutated, the caspase could not be activated.

CTLs mediate a powerful and lethal immune response to infected host cells. Which of the following steps is NOT involved with CTL activation and function?

Histamine is released from cytoplasmic granules recruiting macrophages to the site of infection.

Toxoplasma gondii is a single-celled parasitic protozoan that infects and replicates in macrophages. It is common in the environment, and is transmitted to humans by the ingestion of undercooked meat or by accidental ingestion of the parasite's oocytes from contaminated water or cat litter. Infected individuals with healthy immune systems are generally asymptomatic, and rapidly clear the infection. However, in AIDS patients, infections of Toxoplasma gondii can lead to severe disease and even death. To investigate the immune mechanisms important in controlling Toxoplasma gondii, a mouse model of the infection was developed. Mice were infected with the protozoa at a dose where the majority of the mice survive the infection, and at the same time, were injected with a neutralizing antibody to a cytokine made by T cells (anti-'X' IgG). A second group of mice received the protozoa plus a control IgG antibody, as shown in the figure. Based on this information, the most likely candidate for cytokine 'X' is:

IFN-gamma

Salmonella typhimurium is a Gram-negative bacterial pathogen that infects its host via the gastrointestinal (GI) tract. Early in infection, the bacteria enter and replicate in gut epithelial cells, where the infection induces the development of TH17 cells in the GI tract. However, this response does not eradicate the pathogen, as S. typhimurium has evolved strategies to evade the TH17 response and to spread systemically by infecting and replicating in macrophages. Therefore, a second phase of the immune response is required to completely eliminate the pathogen from the body, as has been demonstrated in mouse models of S. typhimurium infection. These experiments in mouse models likely showed that:

IFN-gamma is required to clear S. typhimurium from the body.

Following an acute virus infection in which the host clears the virus by approximately one week post-infection, a population of virus-specific memory CD8 T cells is maintained and can be detected for months to years post-infection. In mice with a knockout of a single cytokine, however, virus-specific memory CD8 T cells cannot be maintained and disappear over time as shown in the figure below. Base on this information, the most likely identity of the cytokine that is missing in these knockout mice is _____________.

IL-15 NOTE: Yes. The homeostatic mechanisms governing the survival of memory T cells differ from those for naive T cells. Memory T cells divide more frequently than naive T cells, and their expansion is controlled by a shift in the balance between proliferation and cell death. The survival of memory T cells requires signaling by the receptors for the cytokines IL-7 and IL-15. IL-7 is required for the survival of both CD4 and CD8 memory T cells. In addition, IL-15 is critical for the long-term survival and proliferation of CD8 memory T cells under normal conditions. In the absence of IL-15 (or the IL-15R), memory CD8 T cells slowly disappear from the population.

T-cell activation requires antigen being displayed in the context of an APC and interaction between co-stimulatory molecules on the APC and the T cell. In addition to these two signals, T-cell activity is often influenced by cytokines. Which of the following is an example of how cytokines can influence T-cell activity in the presence of MHC presentation and co-stimulatory ligand interaction?

IL-2 triggers T-cell proliferation.

The Bcl-2 protein was first identified based on its over-expression in a subset of B cell lymphomas, where it was shown to promote the resistance of the tumor cells to apoptosis. Sub-cellular localization experiments would show that Bcl-2 is present:

In the mitochondria where it blocks cytochrome c release. NOTE: Yes. Anti-apoptotic Bcl-2 family proteins function by binding to the mitochondrial membrane to block the release of cytochrome c.

Unlike B lymphocytes, T lymphocytes do not generate a secreted form of their antigen receptor after they are activated and proliferate. This is because the effector functions of T cells are restricted to:

Interactions with other cells, such as virus-infected cells or other immune cells

The antigen receptor on a T cell recognizes a degraded fragment of a protein (i.e., a peptide) bound to a specialized cell surface peptide-binding receptor called an MHC molecule. One key aspect of this system is that the peptides displayed on MHC molecules can be derived from intracellular proteins. This mode of antigen recognition is particularly important in allowing the adaptive immune response to detect infections by:

Intracellular pathogens, such as viruses and some protozoa

Secondary (or peripheral) lymphoid organs are sites for initiation of adaptive immune responses. Given the rarity of lymphocytes specific for any given antigen and the vast amount of body tissue that must be protected, the system of secondary lymphoid tissues is efficient because:

It concentrates antigens in centralized locations for rare lymphocytes to encounter

Mycobacterium leprae, the causative agent of leprosy in humans, is an intracellular pathogen that resides in the phagosome of macrophages. Leprosy presents in two main clinical manifestations. Tuberculoid leprosy results in the formation of granulomas and a cell-mediated immune response while lepromatous leprosy results in the production of high levels of IgG (hypergammaglobulinemia). If TH2 is produced in high levels during an leprae infection, which type of leprosy would result?

Lepromatous leprosy

Memory T cells, effector T cells, and naïve T cells share several characteristics. Which of the following descriptions could only be said of memory T cells?

Memory T cells are activated by any APC

A mouse is infected with staphylococcal bacteria through a laceration in the skin of its paw. Dendritic cells are isolated from the tissue at the site of infection, and are incubated together with naïve staphylococcal-specific CD4 T cells. Seventy-two hours later, the proliferation of the CD4 T cells is measured as a readout for T cell activation. Surprisingly, the T cell response is quite poor compared to the response observed when the same T cells are mixed with a comparable number of dendritic cells isolated from the draining lymph node of the infected mouse. A comparison of the dendritic cells isolated from the two different sites would reveal:

Much higher levels of MHC and B7 molecules on the lymph node dendritic cells than those from the infected tissue

Antibody-dependent cell-mediated cytotoxicity (ADCC) is an important effector mechanism in immunity to virus infections. This immune pathway has also been exploited for clinical applications. For instance, patients with various disorders, including rheumatoid arthritis and some B cell lymphomas, are treated with an antibody directed at CD20, a surface receptor expressed on all B cells. This antibody leads to the depletion of B cells from the patients by the actions of:

Natural killer (NK) cells

Inflammatory bowel disease (colitis) is a CD4 T-cell mediated disease that can be transferred to naive mice by administration of effector CD4 T cells that home to the gastrointestinal tract and induce inflammation. Simultaneous administration of neutralizing antibodies to IL-12p40 (a subunit of IL-23) can prevent the disease, as well as neutralizing antibodies to IL-23p19 (another subunit of IL-23). Disease symptoms can be exacerbated by administration of IL-23, but not of IL-12. These data strongly suggest that:

Neutralizing antibodies to IL-17 would prevent disease. NOTE: Yes. The data indicate a key role for TH17 cells and for their dependence on IL-23 to induce disease as the antibody neutralization data shows that both subunits of IL-23 are essential (IL-12p40 and IL-23p19) and that IL-23, but not IL-12, will exacerbate disease.

Most effector T cells migrate out of secondary lymphoid organs and into tissues to exert their function. In which of the cases shown in the figure below will the TH1 effector cell undergo long-lived interactions with its target cell, an infected macrophage? Assume all of the target cells shown below are infected with the pathogen recognized by the specific TH1 cells.

Picture A

Which of the following does NOT occur shortly following oligomerization of the BCR upon antigen binding?

Positioning of CD3 to allow for phosphorylation if its ITAM motifs

When complement proteins are covalently deposited onto the surface of a bacterium, this can sometimes lead to direct lysis of the bacterium. However, more commonly, the deposition of complement proteins onto the bacterial surface does not directly harm the bacterium. Instead, these complement proteins aid in bacterial elimination by:

Providing a mechanism for phagocytes bearing complement receptors to recognize and ingest the bacterium.

The compound LE135 is an inhibitor of the retinoic acid receptor, and blocks signaling through this receptor. In a mouse model of inflammatory bowel disease (IBD), inflammation in the gastrointestinal (GI) epithelium is significantly exacerbated if animals are treated with LE135. Analysis of the CD4 T cell subsets found in the GI epithelium of LE135-treated mice compared to controls with IBD would likely show:

Reduced numbers of iTregs in the LE135-treated mice

For each of the following statements, indicate whether it is true only of B cell epitopes, only of T cell epitopes, or if it is true for both types of epitopes. Assume it is a large antigen. They almost always consist of a linear sequence of amino acids. They are generally located in the interior of a protein antigen They are generally located on the surface of a protein antigen The lose their immunogenecity when a protein antigen is denatured by heat Multiple different epitopes may occur in the same antigen They generally arise from protein antigens Their immunogenecity may depend on the three-dimensional structure of the antigen

T cell epitope T cell epitope B cell epitope B cell epitope BOTH T cell epitope B cell epitope

Which of the following lists the types of cells that act as cytotoxic effector cells?

TC cells, NK-T cells, and NK cells.

In cell culture experiments, purified B cells expressing IgM can be induced to switch to producing IgE by stimulating them with an antibody to CD40 (a stimulatory antibody) plus the cytokine IL-4. In an individual undergoing an immune response, these signals would normally be provided by:

TFH cells in the germinal center

Which type of T helper cell regulates allergic reactions and protects against extracellular pathogens?

TH2

Unlike innate immune responses, adaptive immune responses are initiated in secondary lymphoid organs. However, the innate immune response to an infection in a tissue has a pivotal role in inducing T-cell responses in the nearest lymph node by activating tissue dendritic cells and inducing their migration to the lymph node.

TRUE NOTE: Dendritic cells can be activated via their TLRs and other pathogen-recognition receptors, by tissue damage, or by cytokines produced during the inflammatory response. Activated dendritic cells migrate to the lymph node and express the co-stimulatory molecules that are required, in addition to antigen, for the activation of naive T cells. In the lymphoid tissues, these dendritic cells present antigen to naive T lymphocytes and prime antigen-specific T cells to divide and mature into effector cells that reenter the circulation.

The generation of optimal CD8 T cell memory following a primary infection requires CD4 T cell help for the responding CD8 T cells. This requirement for CD4 T cell help would not be completely replaced by supplying high levels of the cytokine IL-2 during the primary CD8 T cell response.

TRUE NOTE: The mechanism underlying the requirement for CD4 T cells is not completely understood. It may involve two types of signals received by the CD8 T cell, those received through CD40 and those received through the IL-2 receptor. CD8 T cells that do not express CD40 are unable to generate memory T cells. Although many cells could potentially express the CD40 ligand needed to stimulate CD40, it is most likely that CD4 T cells are the source of this signal. Therefore, in addition to providing the cytokine IL-2, CD4 T cells must interact with the responding CD8 T cells to provide CD40 ligand stimulation of CD40 on the CD8 T cells.

Inbred strains of mice often generate highly polarized CD4 T cell responses to specific infections that are dominated by one subset of effector cells. In the case of Balb/c mice infected with the intracellular protozoan Leishmania major, a robust CD4 T cell response is elicited, generating large numbers of L. major-specific T cells; however, this response does not eliminate the pathogen, and instead the mice succumb to the infection. One likely explanation for this finding is:

The CD4 T cell response produces effector cytokines that do not activate macrophages.

Naive T cells are isolated and left untreated or treated with 'compound X' for 1 hour. Following this, the T cells are incubated with a range of concentrations of a soluble form of ICAM-1 that has been conjugated to a fluorescent dye (soluble-ICAM-1-FITC). Fifteen minutes later, the cells are washed, and the relative amount of fluorescence bound to the cells is measured. The results of this assay are shown in the figure below. Based on this data, the most likely identity of Compound X is _________________.

The chemokine ligand for CCR7 NOTE: Yes. Signaling through chemokine receptor CCR7 on naive T cells induces LFA-1 to change conformation to the high-affinity state. This greatly increases its affinity for integrin binding. Therefore, after treatment with the ligand for CCR7 (which is CCL21), naive T cells would show maximal binding to ICAM-1 at a lower concentration of soluble-ICAM-1 than the untreated cells.

Cytotoxic T cells are rapid killers of infected target cells. Within minutes of the interaction of a cytotoxic T cell with a target cell, the program of apoptosis in the target cell is initiated. This rapid activity is a consequence of:

The expression and packaging of perforin and granzymes in cytotoxic granules prior to target cell encounter NOTE: Yes. Cytotoxic T cells can kill their targets rapidly because they store preformed cytotoxic proteins in forms that are inactive in the environment of the cytotoxic granule.

In the cases of some infections, such as mice infected with adenovirus, the generation of effector cytotoxic CD8 T cell responses needed to clear the infection is dependent on the antigen-presenting dendritic cells receiving stimulation through the CD40 receptor on their surface, a process known as dendritic cell 'licensing'. In this infection system, the dendritic cell would likely receive CD40 receptor stimulation from:

The interaction with a CD4 effector cell expressing CD40 ligand

The alternate and classical complement pathways differ in which of the following ways?

The mechanisms initiating activation.

Given the enormous heterogeneity of antigen receptors expressed on the populations of naive B and T lymphocytes, the adaptive immune response relies on a process where a rare lymphocyte binds to antigen and is first induced to proliferate, before it can perform its effector function. For B cells, there is a mechanism that ensures that the specificity of the antibody secreted by the plasma cell will recognize the same pathogen that initially stimulated the B cell antigen receptor and induced B cell proliferation. Which of the following best describes that mechanism?

The naive B cell expresses a membrane-bound form of the antibody as a receptor, and secretes that same antibody when it differentiates into a plasma cell.

A mouse is immunized with a single 9 amino acid peptide derived from the influenza virus. This peptide binds to MHC class I and produces an epitope (peptide:MHC complex) recognized by a small number of naive CD8 T cells in the mouse. The peptide is mixed with CpG oligonucleotides that are ligands for TLR-9. Surprisingly, this immunization regimen generates a very poor cytotoxic CD8 effector response to targets coated with this peptide compared to immunization with a preparation of intact heat-killed influenza virus mixed with CpG oligonucleotides. The enhanced cytotoxic T cell response to the peptide observed following immunization with intact viral particles compared to the peptide alone is due to:

The presence of CD4 T cell epitopes in the intact virus

Unlike somatic hypermutation, class switching occurs in discrete sequence regions upstream of the immunoglobulin heavy chain coding sequences (called switch regions). One key element in directing the enzyme AID to a specific switch region is the opening of the DNA duplex combined with polymerase stalling during active transcription in that region. A second key feature of directing AID to a specific switch region is:

The processed RNA from the switch region guides AID to this site in the DNA

Cytotoxic effector T cells also produce inflammatory cytokines such as IFN-g and TNF-a when their T-cell receptor recognizes peptide:MHC on a target cell. One effect of this cytokine secretion is to enhance the ability of CD8 effector T cells to recognize and kill other infected cells in the nearby vicinity. This enhanced activity is due to:

The up-regulation of MHC class I protein expression by IFN-gamma.

The process of somatic hypermutation of antibody V regions sequences is initiated by the enzyme AID. This enzyme targets cytidine residues in the DNA sequence that are normally part of a G:C pair in the double-stranded DNA. Yet the hypermutation process generates mutations at both G:C and A:T base pairs of the original sequence because:

There are two different repair pathways that have different outcomes, one targeting G:C and one targeting A:T base pairs.

A mouse is immunized with the tetanus toxoid protein (inactivated toxin) in adjuvant. One week later, the entire population of splenic B cells are isolated from the mouse and mixed with tetanus toxoid-specific CD4 TFH cells plus the purified tetanus toxoid protein. Four days later, the total number of B cells in the culture and the number of tetanus toxoid-specific B cells are determined and compared to the starting population on the day of isolation. The results are shown in the figure below. The tetanus-specific B cells preferentially survive and proliferate because INSERT GRAPH PICTURE

They are the only B cells presenting the tetanus peptide to the TFH cells

Studies in mice have shown that resident memory cells (TRM) most often take up permanent residence in the tissue where the initial infection that produced those memory cells occurred. In this location, they are poised to respond rapidly should that infection re-occur in that same location. In contrast, central memory cells (TCM) are primarily found in secondary lymphoid organs, where they can be activated to proliferate and differentiate into effector cells when stimulated by antigen-bearing dendritic cells following re-infection. The third subset of memory cells, effector memory cells (TEM), are recirculating cells that can readily enter tissues at sites of inflammation or infection and are poised to rapidly respond to re-infection. The subset of TEM cells provides an important component of protective immunity to re-infection by the same pathogen because:

They can protect against re-infection that occurs in a different site in the body than the primary infection. NOTE: Yes. While re-infection with the same pathogen often occurs in the same location as the initial primary infection, this is not always the case. Therefore, the circulating effector memory T cells can patrol all tissues in the body, and are not restricted to a single tissue of residence.

Precursor CTLs are characterized by each of the following EXCEPT: they produce low amounts of IL-2. they lack cytotoxic activity. they express CD4. they do not express CD25. they do not divide.

They express CD4

Follicular helper T cells are a recent discovery in the Helper T-cell lineage. What is the primary role of TFH cells?

To help B cell development in germinal centers

What is the function of a memory T cell?

To provide an almost immediate response upon subsequent exposure to a specific pathogen

Which type of T helper cell inhibits inflammation?

Treg

PD-1 is a negative co-stimulatory signal expressed by tumor cells. What advantage would the expression of PD-1 have in a tumor cell avoiding the immune response?

Tumor cells can avoid being killed by activated TC cells.

In a recent experiment, NK cells were collected from an MCMV infected mouse, 50 days after infection, and placed into a healthy mouse. Upon exposure to the MCMV virus, the healthy mouse quickly mounted an immune response. How could these results BEST be interpreted?

What is measured by the cell-mediated lympholysis (CML) assay?

The germinal center is a region within the secondary B cell follicle where sustained B cell proliferation and differentiation take place. The processes of B cell proliferation and differentiation, including affinity maturation and class switching, require periodic interactions of the germinal center B cells with CD4 TFH cells. These periodic interactions between the B cells and TFH cells can occur:

When B cells cycle between the dark zone and the light zone of the germinal center

What is the effector molecule of humoral immunity?

antibodies

Cell mediated immunity includes ________________

both Th and Tc cells

Which complement pathway would be most affected by an absence of RAG1 in developing B cells?

classical

All immunoglobulin molecules on the surface of a given B cell have the same isotype.

false

B cell epitopes can be deduced with great accuracy from the primary structure of a protein

false

Mucosal surfaces and external epithelia are major routes of pathogenic infection. Mucosal surfaces are found in tissues such as the gastrointestinal tract, the reproductive tract and the mouth and respiratory tract. While the mouth and respiratory tract are routes of virus but not bacterial infections, the gastrointestinal tract is the route for bacterial but not virus infections.

false

Our immune system efficiently kills all categories of microbes that attempt to colonize our bodies.

false

All of the following are functions of TH1 cells EXCEPT: can contribute to autoimmunity inhibit anti-tumor responses enhance APC activity. protects against intracellular pathogens. enhance TC activity.

inhibit anti-tumor responses

When vesicular stomatitis virus (VSV) is used to infect mice via footpad injection, viral particles are trapped in the draining lymph node (the popliteal lymph node) within 5 minutes of injection. These viral particles are then retained in the lymph node for many hours, where they can be visualized on cells that are interacting with B cells. The cells retaining the viral particles in the lymph node are not tissue-resident dendritic cells that have migrated to the lymph node with the virus, as this process takes much longer than 5 minutes. In which region of the lymph node would you expect to find the trapped viral particles and on which cells? The virus particles are trapped on___

macrophages in the subcapsular sinus

The skin and bodily secretions provide the first line of defense against infection. One response in this category that is common during upper respiratory virus infections is:

mucus production

TH17 cells are involved with all of the following EXCEPT: protection against bacterial infections. inflammatory response. protection against fungal infections. protection from viral infections. autoimmunity.

protection from viral infections

Licensing on an NK cells refers to:

testing an NK cell to ensure that it will not target healthy host cells.

Which of the following is a location where naïve TC cells could be activated to become CTLs?

the spleen

The role of cell-mediated immunity is:

to find and eliminate cells infected with intracellular pathogens.

A large protein antigen can generally be bound by many different antibody molecules simultaneously

true

A rabbit immunized with human IgG3 will produce antibody that reacts with all subclasses of IgG in humans

true

All immunoglobulin molecules on the surface of a given B cell have the same idiotype.

true

Dendritic cells primarily encounter antigen in peripheral tissues, leading to activation and migration of these tissue dendritic cells to the closest lymph node to activate T cells.

true

For cells of the innate immune system, each individual cell has multiple pattern recognition receptors, allowing it to recognize many different pathogens. In contrast, cells of the adaptive immune system each express a unique antigen receptor that has a single specificity for pathogen recognition.

true

In the absence of an infection, most granulocytes (neutrophils, eosinophils, basophils) are found circulating in the blood, whereas other subsets of myeloid cells reside in tissues.

true

Many B cell epitopes are non-sequential amino acids brought together by the tertiary conformation of a protein antigen.

true

Most antigens induce a response from more than one T cell or B cell (more than one clone, or version of a TCR or BCR).

true

The hypervariable regions make significant contact with epitope

true

The spleen is a secondary lymphoid organ that performs several functions. In addition to its role as a site for initiating adaptive immune responses, the spleen is important in removing dead or damaged red blood cells from the circulation. Its immune function is important because blood-borne pathogens will not be transported to draining lymph nodes via the lymph fluid.

true

Antibodies, complement proteins, and phagocytic cells provide effective protection against all of the following types of infections in the figure below, except ________ [PICTURE]

virus-infected cell

Which of the following is MOST likely to simulate/activate a memory T cell?

Either a B cell, dendritic cell, or a macrophage

While CD28 co-stimulation is important for the initial activation of naive T cells, other co-stimulatory molecules function at later stages of the T cell response. Several of these other co-stimulatory molecules are members of the TNF-receptor family, and function by activating the transcription factor, NFkB. Therefore, stimulation of these co-stimulatory TNF-receptors on activated T cells is likely to:

Enhance T cell survival

At early timepoints following an infection, examination of lymph node CD4 T cells responding to the pathogen would show a heterogeneous population of cells representing several different effector lineages. Likewise, the cytokines produced by these cells would include IFN-gamma, IL-4, and possibly others. However, approximately one week later at the peak of the T cell response, the pathogen-specific CD4 T cell population would be largely homogeneous in their production of a single effector subset cytokine profile. This change comes about due to:

Enhanced differentiation of newly activated CD4 T cells into one effector subset

Initially after an infection, the majority of the T cells present in the tissue at a site of infection are not specific for the infecting pathogen, but over the course of several days, this changes and antigen-specific T cells become enriched at this site. This is because:

Extravasation from blood into tissues is determined by homing molecules, not antigen specificity. NOTE: Yes. In the early stage of the adaptive immune response, only a minority of the effector T cells that enter infected tissues will be specific for pathogen. This is because activation of the endothelium of local blood vessels by inflammatory cytokines induces expression of selectins, integrin ligands, and chemokines that can recruit any circulating effector or memory T cell that expresses the appropriate trafficking receptors, irrespective of its antigenic specificity. However, specificity of the reaction is rapidly increased as the number of pathogen- specific T cells increases and recognition of antigen within the inflamed tissue retains them there.

In a lymph node, nTreg cells are able to inhibit the responses of other T cells in their vicinity. This inhibition is specific, as the nTreg cell and the naive T cell must share the same antigen specificity.

FALSE NOTE: nTreg cells in a lymph node function primarily by acting on antigen-presenting cells to down-regulate their co-stimulatory activity and their inflammatory cytokine production. Based on this mechanism, it is not necessary that the nTreg cell and the naive T cell whose response is inhibited share the same antigen specificity.

Once B cells begin secreting antibodies, they cease dividing and have a life-span of only a few days.

False NOTE: B cells proliferate in the primary focus for several days, and this constitutes the first phase of the primary humoral immune response. Some of these proliferating B cells differentiate into antibody-synthesizing plasmablasts in the primary focus. Plasmablasts are cells that have begun to secrete antibody, yet are still dividing and express many of the characteristics of activated B cells that allow their interaction with T cells.

This complement component can be cleaved by a complex it might be part of:

C3

Which of the following does NOT occur during dendritic cell maturation?

DCs activate T cells by trafficking from lymph nodes to sites of infection.