IMMUNOLOGY EXAM #3 QUESTIONS
WITH VERIFIED ANSWERS
While CD28 co-stimulation is important for the initial activation of naive T cells, other
Cytotoxic T cells that lack expression of perforin are more defective in killing target
cells than those that lack granzymes. - Answer-True
Cytotoxic granules released from cytotoxic T cells contain proteins that enter target
cells and induce apoptosis. Do any of the mechanisms of apoptosis induction by
cytotoxic effector T cells rely on the protein APAF-1? If so, which pathway? -
Answer-Yes - Intrinsic pathway
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: - Answer-The
expression and packaging of perforin and granzymes in cytotoxic granules prior to
target cell encounter
Cytotoxic effector T cells also produce inflammatory cytokines such as IFN- and
TNF- 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: -
Answer-The up-regulation of MHC class I protein expression by IFN-
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 Figure Q10.1. - Answer-
They are the only B cells presenting the tetanus peptide to the TFH cells.
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: - Answer-Antibodies to the
bacterial polysaccharide and the tetanus toxoid
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: - Answer-A defect in T cell-dependent
antibody responses
Patients with the disease X-linked lymphoproliferative syndrome (XLP) lack
expression of the small adapter protein SAP, which associates with receptors of the
SLAM family. One characteristic of this disease is an inability of cytotoxic T cells to
, control infections with a virus, Epstein-Barr virus (EBV), that replicates in B cells.
This defect in control of EBV results from: - Answer-A defect in adhesion of cytotoxic
T cells to EBV-infected B cells
Once B cells begin secreting antibodies, they cease dividing and have a life-span of
only a few days. - Answer-false
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: - Answer-When B cells
cycle between the dark zone and the light zone of the germinal center
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: - Answer-B cells making higher affinity
antibodies receive more help from Tfh cells
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, NFB. Therefore, stimulation of these
co-stimulatory TNF-receptors on activated T cells is likely to: - Answer-Enhance T
cell survival
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: - Answer-The presence of
CD4 T cell epitopes in the intact virus
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: - Answer-The CD4
T cell response produces effector cytokines that do not activate macrophages.
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
WITH VERIFIED ANSWERS
While CD28 co-stimulation is important for the initial activation of naive T cells, other
Cytotoxic T cells that lack expression of perforin are more defective in killing target
cells than those that lack granzymes. - Answer-True
Cytotoxic granules released from cytotoxic T cells contain proteins that enter target
cells and induce apoptosis. Do any of the mechanisms of apoptosis induction by
cytotoxic effector T cells rely on the protein APAF-1? If so, which pathway? -
Answer-Yes - Intrinsic pathway
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: - Answer-The
expression and packaging of perforin and granzymes in cytotoxic granules prior to
target cell encounter
Cytotoxic effector T cells also produce inflammatory cytokines such as IFN- and
TNF- 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: -
Answer-The up-regulation of MHC class I protein expression by IFN-
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 Figure Q10.1. - Answer-
They are the only B cells presenting the tetanus peptide to the TFH cells.
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: - Answer-Antibodies to the
bacterial polysaccharide and the tetanus toxoid
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: - Answer-A defect in T cell-dependent
antibody responses
Patients with the disease X-linked lymphoproliferative syndrome (XLP) lack
expression of the small adapter protein SAP, which associates with receptors of the
SLAM family. One characteristic of this disease is an inability of cytotoxic T cells to
, control infections with a virus, Epstein-Barr virus (EBV), that replicates in B cells.
This defect in control of EBV results from: - Answer-A defect in adhesion of cytotoxic
T cells to EBV-infected B cells
Once B cells begin secreting antibodies, they cease dividing and have a life-span of
only a few days. - Answer-false
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: - Answer-When B cells
cycle between the dark zone and the light zone of the germinal center
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: - Answer-B cells making higher affinity
antibodies receive more help from Tfh cells
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, NFB. Therefore, stimulation of these
co-stimulatory TNF-receptors on activated T cells is likely to: - Answer-Enhance T
cell survival
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: - Answer-The presence of
CD4 T cell epitopes in the intact virus
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: - Answer-The CD4
T cell response produces effector cytokines that do not activate macrophages.
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
