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Immunology Questions with Explanation for Grads
Chapter 1 Overview of the immune system
Chapter 2 Innate immunity
Chapter 3 Adaptive immunity
Chapter 4 Immunogens and antigens
Chapter 5 Antibody structure and function
Chapter 6 Antigen-antibody interactions, immune assays, and experimental systems
Chapter 1 Overview of the immune system
1. The formation of memory immune responses is the objective of
vaccination. Immunological memory is predominantly the function of
which of the following?
a. the complement system.
b. cells bearing pattern-recognition receptor molecules.
c. cells of the adaptive immune system.
d. molecules comprising the chemical barrier.
Well done, you have selected the right answer.
Answer: c. The cells of the adaptive immune system are T- and B-cell lymphocytes. These are
antigen-specific and respond with proliferation (expansion) in response to their antigen. These form
an expanded reservoir of long-lived cells with “memory” for the antigen. Complement and molecules
of the chemical barrier are all without antigen specificity. Cells with pattern-recognition receptors
react broadly to pathogens and do not generate memory.
2. When a child encounters a foreign organism (e.g., streptococcus) for
the first time, he or she can respond with a humoral immune response
specific for that organism. This is because of which of the following?
a. The antigens of the organism instruct unformed antibodies to take shape complementary to
them.
b. The antigens of the organism stimulate clonal expansion of preexisting B cells with receptors
specific for the antigens.
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c. The organism is phagocytosed by macrophages and neutrophils.
d. The organism binds to pattern-recognition molecules on B cells.
Answer: b. This is the clonal selection theory, which applies to both B cells, which produce antibodies,
and T cells, which produce cytokines or initiate cytotoxic mechanisms, all in response to specific
antigen recognized by the cell's antigen-specific receptor. This theory has been proven to be correct,
ending the debate between it and the instructional hypothesis (choice a). Although choice c is itself a
correct statement, it is not related to the question.
3. When a woman whose blood type is Rh negative is pregnant, she is
given rho immune globulin to prevent sensitization to an Rh positive
fetus. This is an example of which of the following? [Questions 35 are
linked]
a. passive immunization.
b. active immunization.
c. adaptive immunity.
d. innate immunity.
No Explanation is available for this question.
4. A child is scratched by a bat. Because of the risk of rabies, the child
is immediately given human rabies immune globulin. This is an
example of which of the following?
a. passive immunization.
b. active immunization.
c. adaptive immunity.
d. innate immunity.
Answer: a. 3 and 4: The objective of passive immunity, giving progenerated antigen-specific
antibodies, is to eliminate the stimulating antigen quickly by providing the specific antibodies. This
may be used (somewhat rarely) to quickly control an infection for which vaccination is unavailable or
not administered on a routine basis, as in question 4, or to prevent sensitization, as in the case of
Rh disparate pregnancies (question 3). In the latter instance the objective is to prevent an adaptive
immune response from developing in the pregnant woman by eliminating the stimulus rapidly.
5. The child described in question 4 is also given rabies vaccine in a
series of four intramuscular injections on days 0, 3, 7, and 14. The
objective is for the child to generate which of the following?
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a. complement components.
b. macrophages specific for the organism.
c. chemical toxins for rabies.
d. rabies-specific IgG.
Well done, you have selected the right answer.
Answer: d. The objective of giving several doses of a vaccine is to generate
highly specific and effective antibody (in this case, IgG) and corresponding
memory cells.
Next question
6. One reason why immune responses to pathogens are polyclonal is
because of which of the following?
a. The pathogen is comprised of a single antigenic determinant.
b. The pathogen contains multiple epitopes.
c. T cells produce cytokines.
d. Macrophages and neutrophils participate in the immune response.
Well done, you have selected the right answer.
Answer: b. An epitope is the smallest portion of an antigen capable of having an immune response
directed against it. Antigens contain multiple epitopes, also called antigenic determinants, each of
which stimulates a specific clone of lymphocytes with the appropriate receptor. Hence, the overall
response is polyclonal.
Chapter 2 Innate immunity
1. You enter a dusty room, feel an itch in your nose, and sneeze.
This is an example of the operation of which of the following
innate immune mechanism?
a. the released granular contents of your granulocytes.
b. the low pH of the environment.
c. the physical barrier produced by hairs.
d. phagocytosis by macrophages.
e. mucus combined with the movement of cilia of the lining cells.
Answer: c. Each area of the respiratory tract has physical, chemical, and/or cellular barriers to
assault by foreign invasion.
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2. Some of the dust particles are not expelled by the sneeze and make
their way further down the respiratory tract but not yet into the alveolar
space. Here their elimination is the job of which of the following?
a. the released granular contents of your granulocytes.
b. the low pH of the environment.
c. the physical barrier produced by hairs.
d. phagocytosis by macrophages.
e. mucus combined with the movement of cilia of the lining cells.
Well done, you have selected the right answer.
Answer: e. Each area of the respiratory tract has physical, chemical, and/or cellular barriers to
assault by foreign invasion.
3. A rare small dust particle reaches the alveolus (small terminal air sac
where gas exchange occurs). At this anatomical site, you are protected
by which of the following?
a. the released granular contents of your granulocytes.
b. the low pH of the environment.
c. the physical barrier produced by hairs.
d. phagocytosis by macrophages.
e. mucus combined with the movement of cilia of the lining cells.
Answer: d. Each area of the respiratory tract has physical, chemical, and/or cellular barriers to
assault by foreign invasion.
4. When they infect a cell, some viruses cause downregulation of the
cell membrane major histocompatibility complex (MHC) class I
molecules. This is a mechanism to evade cytotoxic T cells, which
recognize infected cells displaying virus-derived peptides bound to
MHC. However, downregulation of MHC class I molecules makes the
virally infected cell a target of which of the following?
a. macrophages.
b. neutrophils.
c. natural killer (NK) cells.
d. B cells.
e. dendritic cells.
Sorry, you have selected the wrong answer.
Answer: c. The cytotoxic function of NK cells is inhibited by the recognition of MHC class I via killer-
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cell inhibitory receptors (KIRs). The virally infected cell, expressing little MHC class I on its surface,
is now a target for NK cell killing.
5. Which of the following is a distinction between the innate and
adaptive immune systems?
a. the ability of the cells of only one system to produce cytokines.
b. the capacity for exquisite antigenic specificity in only one system.
c. the capacity of only one system to recognize virally infected cells.
d. the ability of cells of only one system to mediate cell cytotoxicity.
Well done, you have selected the right answer.
Answer: b. Only the adaptive immune system is exquisitely antigen-specific. All other capabilities
listed can be found, with variation, in both the innate and adaptive immune systems.
6. In order for a cell to ingest whole bacteria, the cell may employ which
of the following?
a. pinocytosis.
b. antibodies and/or some complement components.
c. cytokines.
d. KIRs.
Well done, you have selected the right answer.
Answer: b. Antibodies and some complement components act as opsonins, increasing the efficiency
of phagocytosis of the coated particle or organism.
7. When an individual encounters Gram-negative bacteria (if the
organisms survive the physical and chemical barriers), they may be
recognized on first encounter by the innate immune system via which
of the following?
a. antibodies.
b. coagulation cascade components.
c. Toll-like receptors (TLRs).
d. the membrane attack complex (MAC).
Sorry, you have selected the wrong answer.
Answer: c. TLRs 4 and 5 recognize lipopolysaccharide (LPS) and flagellin of Gram-negative bacteria
without prior sensitization. Antibodies are part of the adaptive immune system. The MAC comprises
the terminal components of the complement pathway.
Chapter 3 Adaptive immunity
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1. In order for T cells to respond to the antigen for which they are
specific, they need to recognize which of the following?
a. B cells.
b. the antigenic epitope displayed by MHC molecules.
c. immunoglobulin.
d. cytokines.
Answer: b. As opposed to B cells, which can react to unprocessed antigen, the T-cell receptor
(TCR) is stimulated only if presented with small parts of antigen (epitopes) in the context of MHC
molecules. To respond, the T cell then needs a second, non-antigen-specific, signal via
costimulatory molecules.
2. In order to generate an antigen-specific B-cell receptor (BCR) or TCR,
the pre-B cell and pre-T cell must first do which of the following?
a. encounter antigen.
b. rearrange their DNA for their receptors.
c. splice their mRNA for their receptors.
d. traffic to peripheral lymphoid organs.
Answer: b. The generation of antigen-specific receptors occurs in the primary lymphoid organs, the
bone marrow, and the thymus, where the developing B cell and T cell, respectively, must first
rearrange the genes coding for their receptors. This process is antigen independent.
3. Both the lymph nodes and spleen have germinal centers in which B
cells respond to antigen, produce antibody, and generate plasma cells.
A function unique to the spleen as opposed to other peripheral
lymphoid organs is which of the following?
a. filtration of blood-borne pathogens.
b. production of dendritic cells.
c. production of red blood cells.
d. production of emulsifying agents for fat absorption.
Answer: a. Filtration of blood-borne pathogens is a function of red pulp of the spleen. The red pulp
also filters out aged (effete) red blood cells.
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4. In order for lymphocytes to move into a specific tissuethat is, to
know where to go from the circulationthey express on their surfaces
which of the following?
a. complement receptors.
b. antigen-specific receptors.
c. KIRs.
d. MHC.
e. adhesion molecules.
Answer: e. Cell surface adhesion molecules interact with their receptors on endothelial cells
directing the trafficking of lymphocytes. The expression of adhesion molecules may vary based on
exposure to chemokines in the milieu
5. A 5-year-old child falls and scratches herself and within a few days
has an enlarged lymph node in the area draining the abrasion. The cells
in the lymph node are reacting to the foreign stimulus that entered the
skin and that was transported to the lymph node by which of the
following?
a. immunoglobulin.
b. T cells.
c. dendritic cells.
d. complement receptors.
e. Toll-like receptors.
Answer: c. Dendritic cells are one of the cell types that take up antigen for degradation and
presentation to T cells. They migrate from the skin (where they are called Langerhans cells) to the
draining lymph node.
6. In the lymph node of the child described in question 5, the B cells
that will respond to the antigen will enter the lymph node in which of
the following ways?
a. via high endothelial venules.
b. via efferent lymphatic vessels.
c. from the thoracic duct.
d. from the splenic red pulp.
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Answer: a. The B cells specific for the antigen are not necessarily awaiting its arrival in the draining
lymph node. Rather, antigen-specific naïve B and T cells recirculate through the bloodstream and
lymphatics and are detained in the lymph node where they encounter their antigen. They enter the
lymph node through the high endothelial venules.
Chapter 4 Immunogens and antigens
1. You are a laboratory worker involved in vaccine development
for a specific pathogen. Success would be demonstrated when
you can show that the candidate vaccine elicits an immune
response in vaccinated individuals such that infection cannot be
established when the individual is subsequently exposed to the
pathogen. It is known that there are neutralizing antibodies
directed against a particular surface molecule in individuals who
have recovered from infection with the pathogen under study.
However, when that molecule was isolated and injected into
rabbits as an antigen, it failed to elicit an immune response. The
goal of your project is to modify the antigen to do which of the
following?
a. to become an immunogen.
b. to overcome tolerance.
c. to overcome autoimmunity.
d. to ensure that it can bind to T cells as well as antibody.
e. to become a carrier.
Sorry, you have selected the wrong answer.
Answer: a. This scenario suggests that the molecule is an important target to defend against
establishing infection and that when it is part of the entire organism, it is immunogenic, that
is, can induce an immune response. However, the fact that when isolated the molecule loses
immunogenicity suggests that it is now either too small to induce an immune response (a
property of haptens) or has a limited half-life when injected. The goal is therefore to increase
its immunogenicity and availability by linking it to a protein carrier or including an adjuvant in
the vaccine formulation.
2. A first-year pediatric resident is asked to vaccinate children at a
preparation-for-kindergarten fair. She checks each child's immunization
record and then prepares the syringes with the appropriate vaccines. In
a moment of uncertainty she questions and then confirms the route of
administration to be subcutaneous. This route will allow the antigen to
do which of the following?
a. reach the spleen.
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b. be picked up by Langerhans cells.
c. bind to preexisting antibody.
d. bind to serum albumin.
Well done, you have selected the right answer.
Answer: b. Langerhans cells, which are present in the skin, pick up, process, and present antigen
and move from the skin to the lymph nodes. They are the body's most potent antigen-presenting
cells (APCs)
3. In order to elicit an immune response, a carbohydrate must be which
of the following?
a. degraded.
b. bound to a protein carrier.
c. administered intranasally.
d. made of polysaccharides.
Answer: b. Carbohydrates on their own are not immunogenic because they are not degraded or
presented by antigen-presenting cells and therefore cannot stimulate T cells.
4. A protein antigen may bind to its specific receptor via which of the
following?
a. disulfide bonds.
b. hydroxylation.
c. amino bonds.
d. hydrogen bonds.
Well done, you have selected the right answer.
Answer: d. The interaction between an antigen and its receptor is based on weak attractions, not
covalent bonding.
5. An adjuvant may work by which of the following?
a. binding to the antigen, making it more physically complex.
b. eliciting a cross-reactive immune response.
c. presenting the antigen to the T cells.
d. increasing the half-life of the antigen.
Sorry, you have selected the wrong answer.
Answer: d. As opposed to a carrier, an adjuvant is not bound to the antigen. It acts more as a
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vehicle for the antigen, increasing its bioavailability (half-life) and/or inducing a nonspecific local
inflammatory response that then assists in the response to the antigen of interest.
6. A pediatrician is about to give an infant her first tetanus vaccination.
The first-time parents ask for an explanation of what the shot contains.
The doctor explains that he is giving tetanus toxoid. Which of the
following describes this molecule?
a. It is still toxic but will elicit an immune response.
b. It is derived from an organism related to tetanus.
c. It is the carrier form of the toxin.
d. It is a modified, harmless, but immunogenic form of the toxin.
Answer: d. A toxoid, by definition, is a modified form of a toxin such that it retains immunogenicity
and cross-reactivity with the original molecule but is no longer toxic.
7. In preparation for minor surgery, a 6-year-old child is found to be
blood group A and to have antibodies against blood group B in spite of
never having received blood from any donor. This is due to the body's
natural exposure to certain bacteria. Which of the following terms
describe the bacterial molecules that provoke this immune response?
a. heterophile antigens.
b. homologous antigens.
c. toxoid antigens.
d. adjuvants.
Well done, you have selected the right answer.
Answer: a. Heterophile antigens are substances that have similar 3D structures, in this case to
blood group carbohydrate antigens, and therefore are immunologically cross-reactive.
Chapter 5 Antibody structure and function
1. A patient with multiple myeloma has increased protein levels in
his serum and high protein levels in his urine. Both serum and
urine samples are run on a protein gel electrophoresis. Given that
the protein in his urine is a Bence Jones protein only, you would
expect which of the following?
a. the electrophoretic patterns to show sharp spikes in identical locations for both the
serum and urine.
b. the electrophoretic patterns to show sharp spikes in different locations in the serum
and urine.
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c. the urine electrophoresis to show a sharp spike but the serum to show a broad band in
the gamma region.
d. the urine electrophoresis to show a broad band in the gamma region but the serum to
show a sharp spike.
Answer: b. Bence Jones proteins are by definition dimers of light chain only. In multiple
myeloma most patients produce intact monoclonal immunoglobulin molecules, which can be
detected in the serum, even though only the light chains may be excreted in the urine.
Dimers of light chain only would likely run in a position different from that of intact
immunoglobulin, but both serum and urine would show monoclonal peaks. The serum may
contain dimers of light chain as well as intact monoclonal immunoglobulin if the light chains
are produced in excess. The serum would therefore have two peaks, one corresponding to
the peak in the urine.
2. A 2-year-old child with a sore throat is tested for
antistreptococcal antibody to see if the infection is due to this
bacterium. The child is found to have only IgG antibodies to this
organism with no detectable IgM. This indicates which of the
following?
a. remote, not a current, infection with streptococcus.
b. passive transfer of maternal IgG across the placenta.
c. an immunodeficiency disease in which only IgM is lacking.
d. overwhelming infection with streptococcus.
Answer: a. The presence of IgG indicates that the child was exposed and responded to
streptococcus. This could be entirely in the past. The presence of IgM would be evidence for
a current infection. Maternal IgG transferred across the placenta would no longer be present
at age 2.
3. The sibling of a child with strep throat is tested for antistreptococcal
antibodies and found to have none (neither IgM nor IgG). Which of the
following is one possible interpretation of these results?
a. The sibling has a memory response.
b. The sibling had previous exposure to the bacteria.
c. The sibling was tested during the latent period.
d. The sibling recovered quickly from the infection, already clearing the bacteria.
Answer: c. For a, b, and d, the sibling would have detectable antibody to the bacteria. There is a
latency period of 12 weeks after primary infection when no antibody is detected. This latency
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period is of greater consequence for infections such as HIV and when testing blood donations for
HIV and a variety of other viruses.
4. A patient is treated with humanized monoclonal antibody against his
tumor cells. This antibody molecule is genetically engineered such that
the mouse portion that determines antigen specificity is transcribed
and translated with the remainder of the antibody molecule derived
from human. The portion from mouse antibody would be found in
which of the following?
a. μ chain only.
b. allotype.
c. variable region.
d. kappa chain.
e. isotype.
Well done, you have selected the right answer.
Answer: c. The variable region, contributed by both the heavy and light chain, determines antigen
specificity.
Chapter 6 Antigen-antibody interactions, immune assays, and experimental systems
1. The antigenantibody reaction is used as the basis for many
diagnostic tests investigating human diseases outside the immune
system. A child with a bleeding disorder is suspected of having an
inherited abnormality in von Willebrand's factor. The physician orders a
quantitative monoclonal antibody-based assay and a qualitative
functional assay. The quantitative assay results are within reference
range (normal), whereas the qualitative assay shows a marked
decrease in activity. Which of the following is one possible explanation
for these results?
a. An error was made in the laboratory.
b. The antibody is detecting other cross-reactive molecules in the serum.
c. The cross-linking of the antibody falsely raises the level of antigen measured.
d. The factor has a mutation in its active site but not in the epitope to which the antibody is
directed.
Answer: d. In this child, von Willebrand's factor is present in normal amounts but is inactive due to a
mutation. Because the mutation is not in the site to which the antibody is directed, there would be no
deficiency noted in the quantitative assay.
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2. A patient presents with symptoms suggestive of autoimmune
hemolytic anemia. A direct Coombs test is positive. Which of the
following is a correct interpretation of the test?
a. The patient has autoantibodies in her serum that are directed against her own red blood cells.
b. The patient has anti-Ig antibodies in her serum.
c. The patient's red blood cells have autoantibodies bound to the surfaces.
d. The patient has complement-fixing autoantibodies bound to her red blood cells.
Well done, you have selected the right answer.
Answer: c. By definition, a direct Coombs test is measuring antibodies bound to the red blood cells
in the patient. Choice a is an indirect Coombs test.
3. A patient presents with an increased number of lymphocytes in his
peripheral blood. Which of the following is an appropriate technique to
find out which type of lymphocytes these are?
a. enzyme-linked immunosorbent assay (ELISA).
b. radioimmunoassay (RIA).
c. Western blotting.
d. flow cytometric analysis.
Answer: d. The flow cytometer is used to detect antigens, usually on the surface of cells, based on
the reaction of the cells with fluorescent antibodies. The CD molecules (CD3, CD4, etc.) define
lymphocyte subset type and degree of differentiation and can be detected using specific,
fluorescent-tagged antibodies.
4. A patient's serum is mixed with a known concentration of antigen for
the detection of specific antibodies, and this reaction is measured by
precipitate formation. As the serum is diluted stepwise 1:1 with
phosphate-buffered saline, the strength of the reaction increases rather
than decreases. This is probably due to which of the following?
a. the presence of cross-reactive antibodies.
b. multiple epitopes on the antigen.
c. the presence of polyclonal antibodies.
d. prozone effect.
e. indirect Coombs test positivity.
Answer: d. Aggregation needed to form a precipitate occurs in the zone of equivalence, in which the
proportion of antigen to antibodies is optimal. If the antibodies are in great excess of the antigen,
aggregation does not take place until the antibodies are diluted out.
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Immunology Questions with Explanation for Grads • Chapter 1 Overview of the immune system • Chapter 2 Innate immunity • Chapter 3 Adaptive immunity • Chapter 4 Immunogens and antigens • Chapter 5 Antibody structure and function • Chapter 6 Antigen-antibody interactions, immune assays, and experimental systems • Chapter 1 Overview of the immune system 1. The formation of memory immune responses is the objective of vaccination. Immunological memory is predominantly the function of which of the following? a. the complement system. b. cells bearing pattern-recognition receptor molecules. c. cells of the adaptive immune system. d. molecules comprising the chemical barrier. Well done, you have selected the right answer. Answer: c. The cells of the adaptive immune system are T- and B-cell lymphocytes. These are antigen-specific and respond with proliferation (expansion) in response to their antigen. These form an expanded reservoir of long-lived cells with “memory” for the antigen. Complement and molecules of the chemical barrier are all without antigen specificity. Cells with pattern-recognition receptors react broadly to pathogens and do not generate memory. 2. When a child encounters a foreign organism (e.g., streptococcus) for the first time, he or she can respond with a humoral immune response specific for that organism. This is because of which of the following? a. The antigens of the organism instruct unformed antibodies to take shape complementary to them. b. The antigens of the organism stimulate clonal expansion of preexisting B cells with receptors specific for the antigens. c. The organism is phagocytosed by macrophages and neutrophils. d. The organism binds to pattern-recognition molecules on B cells. Answer: b. This is the clonal selection theory, which applies to both B cells, which produce antibodies, and T cells, which produce cytokines or initiate cytotoxic mechanisms, all in response to specific antigen recognized by the cell's antigen-specific receptor. This theory has been proven to be correct, ending the debate between it and the instructional hypothesis (choice a). Although choice c is itself a correct statement, it is not related to the question. 3. When a woman whose blood type is Rh negative is pregnant, she is given rho immune globulin to prevent sensitization to an Rh positive fetus. This is an example of which of the following? [Questions 3–5 are linked] a. passive immunization. b. active immunization. c. adaptive immunity. d. innate immunity. No Explanation is available for this question. 4. A child is scratched by a bat. Because of the risk of rabies, the child is immediately given human rabies immune globulin. This is an example of which of the following? a. passive immunization. b. active immunization. c. adaptive immunity. d. innate immunity. Answer: a. 3 and 4: The objective of passive immunity, giving progenerated antigen-specific antibodies, is to eliminate the stimulating antigen quickly by providing the specific antibodies. This may be used (somewhat rarely) to quickly control an infection for which vaccination is unavailable or not administered on a routine basis, as in question 4, or to prevent sensitization, as in the case of Rh disparate pregnancies (question 3). In the latter instance the objective is to prevent an adaptive immune response from developing in the pregnant woman by eliminating the stimulus rapidly. 5. The child described in question 4 is also given rabies vaccine in a series of four intramuscular injections on days 0, 3, 7, and 14. The objective is for the child to generate which of the following? a. complement components. b. macrophages specific for the organism. c. chemical toxins for rabies. d. rabies-specific IgG. Well done, you have selected the right answer. Answer: d. The objective of giving several doses of a vaccine is to generate highly specific and effective antibody (in this case, IgG) and corresponding memory cells. Next question 6. One reason why immune responses to pathogens are polyclonal is because of which of the following? a. The pathogen is comprised of a single antigenic determinant. b. The pathogen contains multiple epitopes. c. T cells produce cytokines. d. Macrophages and neutrophils participate in the immune response. Well done, you have selected the right answer. Answer: b. An epitope is the smallest portion of an antigen capable of having an immune response directed against it. Antigens contain multiple epitopes, also called antigenic determinants, each of which stimulates a specific clone of lymphocytes with the appropriate receptor. Hence, the overall response is polyclonal. • Chapter 2 Innate immunity • 1. You enter a dusty room, feel an itch in your nose, and sneeze. This is an example of the operation of which of the following innate immune mechanism? • a. the released granular contents of your granulocytes. • b. the low pH of the environment. • c. the physical barrier produced by hairs. • d. phagocytosis by macrophages. • e. mucus combined with the movement of cilia of the lining cells. Answer: c. Each area of the respiratory tract has physical, chemical, and/or cellular barriers to assault by foreign invasion. 2. Some of the dust particles are not expelled by the sneeze and make their way further down the respiratory tract but not yet into the alveolar space. Here their elimination is the job of which of the following? a. the released granular contents of your granulocytes. b. the low pH of the environment. c. the physical barrier produced by hairs. d. phagocytosis by macrophages. e. mucus combined with the movement of cilia of the lining cells. Well done, you have selected the right answer. Answer: e. Each area of the respiratory tract has physical, chemical, and/or cellular barriers to assault by foreign invasion. 3. A rare small dust particle reaches the alveolus (small terminal air sac where gas exchange occurs). At this anatomical site, you are protected by which of the following? a. the released granular contents of your granulocytes. b. the low pH of the environment. c. the physical barrier produced by hairs. d. phagocytosis by macrophages. e. mucus combined with the movement of cilia of the lining cells. Answer: d. Each area of the respiratory tract has physical, chemical, and/or cellular barriers to assault by foreign invasion. 4. When they infect a cell, some viruses cause downregulation of the cell membrane major histocompatibility complex (MHC) class I molecules. This is a mechanism to evade cytotoxic T cells, which recognize infected cells displaying virus-derived peptides bound to MHC. However, downregulation of MHC class I molecules makes the virally infected cell a target of which of the following? a. macrophages. b. neutrophils. c. natural killer (NK) cells. d. B cells. e. dendritic cells. Sorry, you have selected the wrong answer. Answer: c. The cytotoxic function of NK cells is inhibited by the recognition of MHC class I via killer- cell inhibitory receptors (KIRs). The virally infected cell, expressing little MHC class I on its surface, is now a target for NK cell killing. 5. Which of the following is a distinction between the innate and adaptive immune systems? a. the ability of the cells of only one system to produce cytokines. b. the capacity for exquisite antigenic specificity in only one system. c. the capacity of only one system to recognize virally infected cells. d. the ability of cells of only one system to mediate cell cytotoxicity. Well done, you have selected the right answer. Answer: b. Only the adaptive immune system is exquisitely antigen-specific. All other capabilities listed can be found, with variation, in both the innate and adaptive immune systems. 6. In order for a cell to ingest whole bacteria, the cell may employ which of the following? a. pinocytosis. b. antibodies and/or some complement components. c. cytokines. d. KIRs. Well done, you have selected the right answer. Answer: b. Antibodies and some complement components act as opsonins, increasing the efficiency of phagocytosis of the coated particle or organism. 7. When an individual encounters Gram-negative bacteria (if the organisms survive the physical and chemical barriers), they may be recognized on first encounter by the innate immune system via which of the following? a. antibodies. b. coagulation cascade components. c. Toll-like receptors (TLRs). d. the membrane attack complex (MAC). Sorry, you have selected the wrong answer. Answer: c. TLRs 4 and 5 recognize lipopolysaccharide (LPS) and flagellin of Gram-negative bacteria without prior sensitization. Antibodies are part of the adaptive immune system. The MAC comprises the terminal components of the complement pathway. • Chapter 3 Adaptive immunity • 1. In order for T cells to respond to the antigen for which they are specific, they need to recognize which of the following? • a. B cells. • b. the antigenic epitope displayed by MHC molecules. • c. immunoglobulin. • d. cytokines. Answer: b. As opposed to B cells, which can react to unprocessed antigen, the T-cell receptor (TCR) is stimulated only if presented with small parts of antigen (epitopes) in the context of MHC molecules. To respond, the T cell then needs a second, non-antigen-specific, signal via costimulatory molecules. 2. In order to generate an antigen-specific B-cell receptor (BCR) or TCR, the pre-B cell and pre-T cell must first do which of the following? a. encounter antigen. b. rearrange their DNA for their receptors. c. splice their mRNA for their receptors. d. traffic to peripheral lymphoid organs. Answer: b. The generation of antigen-specific receptors occurs in the primary lymphoid organs, the bone marrow, and the thymus, where the developing B cell and T cell, respectively, must first rearrange the genes coding for their receptors. This process is antigen independent. 3. Both the lymph nodes and spleen have germinal centers in which B cells respond to antigen, produce antibody, and generate plasma cells. A function unique to the spleen as opposed to other peripheral lymphoid organs is which of the following? a. filtration of blood-borne pathogens. b. production of dendritic cells. c. production of red blood cells. d. production of emulsifying agents for fat absorption. Answer: a. Filtration of blood-borne pathogens is a function of red pulp of the spleen. The red pulp also filters out aged (effete) red blood cells. 4. In order for lymphocytes to move into a specific tissue—that is, to know where to go from the circulation—they express on their surfaces which of the following? a. complement receptors. b. antigen-specific receptors. c. KIRs. d. MHC. e. adhesion molecules. Answer: e. Cell surface adhesion molecules interact with their receptors on endothelial cells directing the trafficking of lymphocytes. The expression of adhesion molecules may vary based on exposure to chemokines in the milieu 5. A 5-year-old child falls and scratches herself and within a few days has an enlarged lymph node in the area draining the abrasion. The cells in the lymph node are reacting to the foreign stimulus that entered the skin and that was transported to the lymph node by which of the following? a. immunoglobulin. b. T cells. c. dendritic cells. d. complement receptors. e. Toll-like receptors. Answer: c. Dendritic cells are one of the cell types that take up antigen for degradation and presentation to T cells. They migrate from the skin (where they are called Langerhans cells) to the draining lymph node. 6. In the lymph node of the child described in question 5, the B cells that will respond to the antigen will enter the lymph node in which of the following ways? a. via high endothelial venules. b. via efferent lymphatic vessels. c. from the thoracic duct. d. from the splenic red pulp. Answer: a. The B cells specific for the antigen are not necessarily awaiting its arrival in the draining lymph node. Rather, antigen-specific naïve B and T cells recirculate through the bloodstream and lymphatics and are detained in the lymph node where they encounter their antigen. They enter the lymph node through the high endothelial venules. • Chapter 4 Immunogens and antigens • 1. You are a laboratory worker involved in vaccine development for a specific pathogen. Success would be demonstrated when you can show that the candidate vaccine elicits an immune response in vaccinated individuals such that infection cannot be established when the individual is subsequently exposed to the pathogen. It is known that there are neutralizing antibodies directed against a particular surface molecule in individuals who have recovered from infection with the pathogen under study. However, when that molecule was isolated and injected into rabbits as an antigen, it failed to elicit an immune response. The goal of your project is to modify the antigen to do which of the following? • a. to become an immunogen. • b. to overcome tolerance. • c. to overcome autoimmunity. • d. to ensure that it can bind to T cells as well as antibody. • e. to become a carrier. • Sorry, you have selected the wrong answer. Answer: a. This scenario suggests that the molecule is an important target to defend against establishing infection and that when it is part of the entire organism, it is immunogenic, that is, can induce an immune response. However, the fact that when isolated the molecule loses immunogenicity suggests that it is now either too small to induce an immune response (a property of haptens) or has a limited half-life when injected. The goal is therefore to increase its immunogenicity and availability by linking it to a protein carrier or including an adjuvant in the vaccine formulation. 2. A first-year pediatric resident is asked to vaccinate children at a preparation-for-kindergarten fair. She checks each child's immunization record and then prepares the syringes with the appropriate vaccines. In a moment of uncertainty she questions and then confirms the route of administration to be subcutaneous. This route will allow the antigen to do which of the following? a. reach the spleen. b. be picked up by Langerhans cells. c. bind to preexisting antibody. d. bind to serum albumin. Well done, you have selected the right answer. Answer: b. Langerhans cells, which are present in the skin, pick up, process, and present antigen and move from the skin to the lymph nodes. They are the body's most potent antigen-presenting cells (APCs) 3. In order to elicit an immune response, a carbohydrate must be which of the following? a. degraded. b. bound to a protein carrier. c. administered intranasally. d. made of polysaccharides. Answer: b. Carbohydrates on their own are not immunogenic because they are not degraded or presented by antigen-presenting cells and therefore cannot stimulate T cells. 4. A protein antigen may bind to its specific receptor via which of the following? a. disulfide bonds. b. hydroxylation. c. amino bonds. d. hydrogen bonds. Well done, you have selected the right answer. Answer: d. The interaction between an antigen and its receptor is based on weak attractions, not covalent bonding. 5. An adjuvant may work by which of the following? a. binding to the antigen, making it more physically complex. b. eliciting a cross-reactive immune response. c. presenting the antigen to the T cells. d. increasing the half-life of the antigen. Sorry, you have selected the wrong answer. Answer: d. As opposed to a carrier, an adjuvant is not bound to the antigen. It acts more as a vehicle for the antigen, increasing its bioavailability (half-life) and/or inducing a nonspecific local inflammatory response that then assists in the response to the antigen of interest. 6. A pediatrician is about to give an infant her first tetanus vaccination. The first-time parents ask for an explanation of what the shot contains. The doctor explains that he is giving tetanus toxoid. Which of the following describes this molecule? a. It is still toxic but will elicit an immune response. b. It is derived from an organism related to tetanus. c. It is the carrier form of the toxin. d. It is a modified, harmless, but immunogenic form of the toxin. Answer: d. A toxoid, by definition, is a modified form of a toxin such that it retains immunogenicity and cross-reactivity with the original molecule but is no longer toxic. 7. In preparation for minor surgery, a 6-year-old child is found to be blood group A and to have antibodies against blood group B in spite of never having received blood from any donor. This is due to the body's natural exposure to certain bacteria. Which of the following terms describe the bacterial molecules that provoke this immune response? a. heterophile antigens. b. homologous antigens. c. toxoid antigens. d. adjuvants. Well done, you have selected the right answer. Answer: a. Heterophile antigens are substances that have similar 3D structures, in this case to blood group carbohydrate antigens, and therefore are immunologically cross-reactive. • Chapter 5 Antibody structure and function • 1. A patient with multiple myeloma has increased protein levels in his serum and high protein levels in his urine. Both serum and urine samples are run on a protein gel electrophoresis. Given that the protein in his urine is a Bence Jones protein only, you would expect which of the following? • a. the electrophoretic patterns to show sharp spikes in identical locations for both the serum and urine. • b. the electrophoretic patterns to show sharp spikes in different locations in the serum and urine. • c. the urine electrophoresis to show a sharp spike but the serum to show a broad band in the gamma region. • d. the urine electrophoresis to show a broad band in the gamma region but the serum to show a sharp spike. • Answer: b. Bence Jones proteins are by definition dimers of light chain only. In multiple myeloma most patients produce intact monoclonal immunoglobulin molecules, which can be detected in the serum, even though only the light chains may be excreted in the urine. Dimers of light chain only would likely run in a position different from that of intact immunoglobulin, but both serum and urine would show monoclonal peaks. The serum may contain dimers of light chain as well as intact monoclonal immunoglobulin if the light chains are produced in excess. The serum would therefore have two peaks, one corresponding to the peak in the urine. • 2. A 2-year-old child with a sore throat is tested for antistreptococcal antibody to see if the infection is due to this bacterium. The child is found to have only IgG antibodies to this organism with no detectable IgM. This indicates which of the following? • a. remote, not a current, infection with streptococcus. • b. passive transfer of maternal IgG across the placenta. • c. an immunodeficiency disease in which only IgM is lacking. • d. overwhelming infection with streptococcus. • Answer: a. The presence of IgG indicates that the child was exposed and responded to streptococcus. This could be entirely in the past. The presence of IgM would be evidence for a current infection. Maternal IgG transferred across the placenta would no longer be present at age 2. 3. The sibling of a child with strep throat is tested for antistreptococcal antibodies and found to have none (neither IgM nor IgG). Which of the following is one possible interpretation of these results? a. The sibling has a memory response. b. The sibling had previous exposure to the bacteria. c. The sibling was tested during the latent period. d. The sibling recovered quickly from the infection, already clearing the bacteria. Answer: c. For a, b, and d, the sibling would have detectable antibody to the bacteria. There is a latency period of 1–2 weeks after primary infection when no antibody is detected. This latency period is of greater consequence for infections such as HIV and when testing blood donations for HIV and a variety of other viruses. 4. A patient is treated with humanized monoclonal antibody against his tumor cells. This antibody molecule is genetically engineered such that the mouse portion that determines antigen specificity is transcribed and translated with the remainder of the antibody molecule derived from human. The portion from mouse antibody would be found in which of the following? a. μ chain only. b. allotype. c. variable region. d. kappa chain. e. isotype. Well done, you have selected the right answer. Answer: c. The variable region, contributed by both the heavy and light chain, determines antigen specificity. • Chapter 6 Antigen-antibody interactions, immune assays, and experimental systems 1. The antigen–antibody reaction is used as the basis for many diagnostic tests investigating human diseases outside the immune system. A child with a bleeding disorder is suspected of having an inherited abnormality in von Willebrand's factor. The physician orders a quantitative monoclonal antibody-based assay and a qualitative functional assay. The quantitative assay results are within reference range (normal), whereas the qualitative assay shows a marked decrease in activity. Which of the following is one possible explanation for these results? a. An error was made in the laboratory. b. The antibody is detecting other cross-reactive molecules in the serum. c. The cross-linking of the antibody falsely raises the level of antigen measured. d. The factor has a mutation in its active site but not in the epitope to which the antibody is directed. Answer: d. In this child, von Willebrand's factor is present in normal amounts but is inactive due to a mutation. Because the mutation is not in the site to which the antibody is directed, there would be no deficiency noted in the quantitative assay. 2. A patient presents with symptoms suggestive of autoimmune hemolytic anemia. A direct Coombs test is positive. Which of the following is a correct interpretation of the test? a. The patient has autoantibodies in her serum that are directed against her own red blood cells. b. The patient has anti-Ig antibodies in her serum. c. The patient's red blood cells have autoantibodies bound to the surfaces. d. The patient has complement-fixing autoantibodies bound to her red blood cells. Well done, you have selected the right answer. Answer: c. By definition, a direct Coombs test is measuring antibodies bound to the red blood cells in the patient. Choice a is an indirect Coombs test. 3. A patient presents with an increased number of lymphocytes in his peripheral blood. Which of the following is an appropriate technique to find out which type of lymphocytes these are? a. enzyme-linked immunosorbent assay (ELISA). b. radioimmunoassay (RIA). c. Western blotting. d. flow cytometric analysis. Answer: d. The flow cytometer is used to detect antigens, usually on the surface of cells, based on the reaction of the cells with fluorescent antibodies. The CD molecules (CD3, CD4, etc.) define lymphocyte subset type and degree of differentiation and can be detected using specific, fluorescent-tagged antibodies. 4. A patient's serum is mixed with a known concentration of antigen for the detection of specific antibodies, and this reaction is measured by precipitate formation. As the serum is diluted stepwise 1:1 with phosphate-buffered saline, the strength of the reaction increases rather than decreases. This is probably due to which of the following? a. the presence of cross-reactive antibodies. b. multiple epitopes on the antigen. c. the presence of polyclonal antibodies. d. prozone effect. e. indirect Coombs test positivity. Answer: d. Aggregation needed to form a precipitate occurs in the zone of equivalence, in which the proportion of antigen to antibodies is optimal. If the antibodies are in great excess of the antigen, aggregation does not take place until the antibodies are diluted out. Name: Description: ...
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