L2300: PQs for Final Exam 2022 with complete solution
List two sensor systems of the innate defenses.
Pattern recognition receptors
Complement system
Describe the dual roles played by some types of phagocytes.
They destroy invaders and also communicate with components of the adaptive immune
system to enlist their help.
What molecules might pattern recognition receptors recognize?
PTG, LPS, flagelin
How does the mucociliary escalator protect against infection?
It moves microbes out of the airways.
What is the role of lactoferrin?
It binds iron, removing it as an element source that would otherwise support microbial
growth.
How would damage to the ciliated cells of the respiratory tract predispose a
person to infection?
The mucociliary escalator would no longer function properly, so microbes wouldn't be
removed from the airways.
Which type of granulocyte is the most abundant?
Neutrophils
How are macrophages related to monocytes?
Macrophages descend from monocytes; the monocytes circulate in blood, and as they
enter the tissues, they develop into macrophages.
Why can bone marrow transplants be used to replace defective lymphocytes?
Bone marrow has hematopoietic stem cells; in the procedure for a bone marrow
transplant, the lymphocytes are destroyed and then another person's bone marrow
(containing hematopoietic stem cells) is transferred. The transferred stem cells can
develop into new lymphocytes (as well as other blood cells).
What is a ligand?
The molecule that binds to a given receptor
What is the function of a colony-stimulating factor (CSF)?
It promotes the development of certain cell types.
How could colony-stimulating factors be used as a therapy?
It can be used to direct the accumulation of a given cell type.
Why would macrophages have TLRs in their endosomal membranes?
So they can determine if they have engulfed microbial invaders (as opposed to normal
host components).
If a cell produces antiviral proteins, what happens to that cell when those
proteins encounter long dsRNA?
The cell shuts down protein synthesis, eventually leading to apoptosis.
Why would the discovery of TLRs alter the view that innate immunity is non-
specific?
Because they allow cells to detect patterns associated with microbes, indicating that the
responses involve some specificity (although not the molecular specificity that
characterizes the adaptive responses).
,What role does C3b play in opsonization and complement system activation?
When many molecules of C3b are bound to a particle, macrophages can more easily
engulf the particle (opsonization); when even a few molecules of C3b are bound to a
particle, other complement components can bind, leading to activation of the
complement system.
The body's own cells do not trigger the alternative pathway of complement
pathway activation. How come?
Molecules in host cell membranes bind regulatory proteins that will inactivate any C3b
molecules that attach to the membrane.
From a pathogen's standpoint, why would it be beneficial to bind regulatory
proteins that inactivate C3b?
It prevents both opsonization and complement activation.
How does a phagolysosome differ from a phagosome?
Phagolysosomes have fused with lysosomes, and therefore they contain the enzymes
and toxic substances of lysosomes.
Tuberculosis is characterized by granulomas called tubercles. What is a
granuloma?
A concentrated group of macrophages, giant cells, and T cells that surrounds microbes
or material that cannot be destroyed
What could a microorganism do to avoid engulfment?
Destroy C5a (a complement protein that attracts phagocytes), destroy phagocytes,
attract complement regulatory proteins to avoid the opsonizing effects co complement.
Describe two general events that can initiate inflammation.
Invasion by microorganisms and tissue damage
Describe two changes in cells undergoing apoptosis
Enzymes cut the DNA and portions of the cell bud off
Infection of the fallopian tubes can lead to infertility. Why would this be so?
Damaged tissue is replaced by scar tissue, which can block a fallopian tube.
What are endogenous and exogenous pyrogens?
Substances that induce fever; cytokines are endogenous pyrogens whereas microbial
products are exogenous pyrogens
How does fever inhibit the growth of pathogens?
A temperature above a microbe's optimum growth temperature can cause the growth
rate to decline sharply.
Syphilis was once treated by infecting the patient with the parasite that causes
malaria, a disease characterized by repeated bouts of fever, shaking, and chills.
Why would this treatment cure syphilis?
The high fever that develops as a result of malaria is above the optimum growth
temperature of the bacterium that causes syphilis.
How is the strategy of the cell-mediated response different from that of the
humoral response?
The humoral response is geared towards eliminating invaders that are in body fluids
whereas the cell-mediated is directed towards eliminating invaders that are within host
cells.
Why is it important that B cells and T cells are activated before they can mount a
response against antigen?
,To ensure that they do not mount a response against the body's own tissues
How is lymph formed?
Fluids and leukocytes from the tissue enter the lymphatic system, becoming lymph.
What are Peyer's patches?
Secondary lymphoid organs where cells of the immune system gather to encounter
material from the intestinal tract.
How would mucosal immunity prevent diarrheal disease?
It neutralizes virus and toxins in the intestinal tract and prevents microorganisms from
traveling through mucus and adhering to the mucous membranes, thereby blocking the
action of intestinal pathogens.
How is an epitope different from an antigen?
An epitope is a very small part of an antigen; B and T cell receptors bind to epitopes on
antigens.
Would a denatured antigen be expected to have the same epitopes as its native
(undenatured) counterpart?
No, because epitopes can be three-dimensional shapes, and those are destroyed when
the protein is denatured.
Why is IgM particularly effective at cross-linking antigens?
It is a pentamer, and therefore has 10 antigen-binding sites.
Which maternal antibody classes protect a breast-fed newborn?
IgG and IgA
In opsonization with IgG, why is it important that phagocytes recognize the
antibodies only after they bind antigen?
For one thing, if phagocytes attached to antibodies before they attached to antigen, the
antibodies would no longer diffuse in tissue fluids and therefore would not neutralize
antigens. Also, the binding would block the Fc portion of antibodies, so the molecules
could never activate the complement system or induce ADCC.
Describe the clonal selection theory.
Each B cell is programmed to recognize a single epitope, and therefore antigens with
that epitope "select" which B cells will respond. In response to this selection, the B cells
divide, producing clones that recognize the same epitope.
How does a naive lymphocyte differ from an activated one?
A naive lymphocyte has never "seen" the epitope to which it is programmed to respond.
Activated lymphocytes have encountered the epitope and have received any required
accessory signals.
Name three types of antigen-presenting cells (APC)
Dendritic cells, macrophages, and B cells
Each of the following statements concerning gonorrhea is correct EXCEPT:
A. Infection in men is more frequently symptomatic than in women.
B. The definitive diagnosis can be made by detecting antibodies to Neisseria
gonorrhoeae in the patient's serum.
C. A presumptive diagnosis can be made by finding gram-negative kidney bean
shaped diplococci within neutrophils in a urethral discharge.
D. Anorectal and pharyngeal infections are important sources of the organism.
E. Gonococcal conjunctivitis of the newborn rarely occurs in the US because
silver nitrate or erythromycin is commonly used as prophylaxis.
, B. The definitive diagnosis can be made by detecting antibodies to Neisseria
gonorrhoeae in the patient's serum.
The herpesviruses are able to evade the host's immune response by which
mechanism?
A. Block interferon production
B. Prevent CD8 T-cell killing
C. Block IL-1 and TNF-mediated inflammation
D. Cause genetic change after infection
E. Establish latent infections
E. Establish latent infections
Each of the following statements about HIV is correct EXCEPT:
A. A DNA copy of the HIV genome integrates into host cell DNA.
B. Acyclovir inhibits HIV replication
C. HIV is an enveloped RNA virus
D. The virion contains an RNA-dependent DNA polymerase
B. Acyclovir inhibits HIV replication
Which of the following is a widely used nontreponemal serologic test?
A. RPR
B. Dark field microscopy
C. MHA-TP
D. FTA-ABS
E. TP-PA
A. RPR
Which cell type would NOT be present in a boy born without a thymus?
A. T cell
B. Macrophages
C. NK cell
D. B cell
E. Neutrophils
A. T cell
During a medical check-up for a new insurance policy, a 60 YO grandmother is
found to be positive in the ELISA screening test for antibodies against HIV-1
infection. She has no known risk factors for exposure to the virus. Which of the
following is the mots appropriate next step?
A. Test the patient for Pneumocystis jiroveci infection
B. Immediately begin therapy with azidothymidine
C. Tell the patient that she is likely to develop AIDS
D. Perform the screening test a second time
E. Request that blood culture be performed in a laboratory
D. Perform the screening test a second time
How can a B cell be distinguished from a T cell?
A. T cells mature in the bone marrow
B. Extensive gene recombinations occur in B cells
C. B cells have surface immunoglobulin
D. B cells have a large nucleus-to-cytoplasm ratio
E. B cells have a sheep RBC receptor
List two sensor systems of the innate defenses.
Pattern recognition receptors
Complement system
Describe the dual roles played by some types of phagocytes.
They destroy invaders and also communicate with components of the adaptive immune
system to enlist their help.
What molecules might pattern recognition receptors recognize?
PTG, LPS, flagelin
How does the mucociliary escalator protect against infection?
It moves microbes out of the airways.
What is the role of lactoferrin?
It binds iron, removing it as an element source that would otherwise support microbial
growth.
How would damage to the ciliated cells of the respiratory tract predispose a
person to infection?
The mucociliary escalator would no longer function properly, so microbes wouldn't be
removed from the airways.
Which type of granulocyte is the most abundant?
Neutrophils
How are macrophages related to monocytes?
Macrophages descend from monocytes; the monocytes circulate in blood, and as they
enter the tissues, they develop into macrophages.
Why can bone marrow transplants be used to replace defective lymphocytes?
Bone marrow has hematopoietic stem cells; in the procedure for a bone marrow
transplant, the lymphocytes are destroyed and then another person's bone marrow
(containing hematopoietic stem cells) is transferred. The transferred stem cells can
develop into new lymphocytes (as well as other blood cells).
What is a ligand?
The molecule that binds to a given receptor
What is the function of a colony-stimulating factor (CSF)?
It promotes the development of certain cell types.
How could colony-stimulating factors be used as a therapy?
It can be used to direct the accumulation of a given cell type.
Why would macrophages have TLRs in their endosomal membranes?
So they can determine if they have engulfed microbial invaders (as opposed to normal
host components).
If a cell produces antiviral proteins, what happens to that cell when those
proteins encounter long dsRNA?
The cell shuts down protein synthesis, eventually leading to apoptosis.
Why would the discovery of TLRs alter the view that innate immunity is non-
specific?
Because they allow cells to detect patterns associated with microbes, indicating that the
responses involve some specificity (although not the molecular specificity that
characterizes the adaptive responses).
,What role does C3b play in opsonization and complement system activation?
When many molecules of C3b are bound to a particle, macrophages can more easily
engulf the particle (opsonization); when even a few molecules of C3b are bound to a
particle, other complement components can bind, leading to activation of the
complement system.
The body's own cells do not trigger the alternative pathway of complement
pathway activation. How come?
Molecules in host cell membranes bind regulatory proteins that will inactivate any C3b
molecules that attach to the membrane.
From a pathogen's standpoint, why would it be beneficial to bind regulatory
proteins that inactivate C3b?
It prevents both opsonization and complement activation.
How does a phagolysosome differ from a phagosome?
Phagolysosomes have fused with lysosomes, and therefore they contain the enzymes
and toxic substances of lysosomes.
Tuberculosis is characterized by granulomas called tubercles. What is a
granuloma?
A concentrated group of macrophages, giant cells, and T cells that surrounds microbes
or material that cannot be destroyed
What could a microorganism do to avoid engulfment?
Destroy C5a (a complement protein that attracts phagocytes), destroy phagocytes,
attract complement regulatory proteins to avoid the opsonizing effects co complement.
Describe two general events that can initiate inflammation.
Invasion by microorganisms and tissue damage
Describe two changes in cells undergoing apoptosis
Enzymes cut the DNA and portions of the cell bud off
Infection of the fallopian tubes can lead to infertility. Why would this be so?
Damaged tissue is replaced by scar tissue, which can block a fallopian tube.
What are endogenous and exogenous pyrogens?
Substances that induce fever; cytokines are endogenous pyrogens whereas microbial
products are exogenous pyrogens
How does fever inhibit the growth of pathogens?
A temperature above a microbe's optimum growth temperature can cause the growth
rate to decline sharply.
Syphilis was once treated by infecting the patient with the parasite that causes
malaria, a disease characterized by repeated bouts of fever, shaking, and chills.
Why would this treatment cure syphilis?
The high fever that develops as a result of malaria is above the optimum growth
temperature of the bacterium that causes syphilis.
How is the strategy of the cell-mediated response different from that of the
humoral response?
The humoral response is geared towards eliminating invaders that are in body fluids
whereas the cell-mediated is directed towards eliminating invaders that are within host
cells.
Why is it important that B cells and T cells are activated before they can mount a
response against antigen?
,To ensure that they do not mount a response against the body's own tissues
How is lymph formed?
Fluids and leukocytes from the tissue enter the lymphatic system, becoming lymph.
What are Peyer's patches?
Secondary lymphoid organs where cells of the immune system gather to encounter
material from the intestinal tract.
How would mucosal immunity prevent diarrheal disease?
It neutralizes virus and toxins in the intestinal tract and prevents microorganisms from
traveling through mucus and adhering to the mucous membranes, thereby blocking the
action of intestinal pathogens.
How is an epitope different from an antigen?
An epitope is a very small part of an antigen; B and T cell receptors bind to epitopes on
antigens.
Would a denatured antigen be expected to have the same epitopes as its native
(undenatured) counterpart?
No, because epitopes can be three-dimensional shapes, and those are destroyed when
the protein is denatured.
Why is IgM particularly effective at cross-linking antigens?
It is a pentamer, and therefore has 10 antigen-binding sites.
Which maternal antibody classes protect a breast-fed newborn?
IgG and IgA
In opsonization with IgG, why is it important that phagocytes recognize the
antibodies only after they bind antigen?
For one thing, if phagocytes attached to antibodies before they attached to antigen, the
antibodies would no longer diffuse in tissue fluids and therefore would not neutralize
antigens. Also, the binding would block the Fc portion of antibodies, so the molecules
could never activate the complement system or induce ADCC.
Describe the clonal selection theory.
Each B cell is programmed to recognize a single epitope, and therefore antigens with
that epitope "select" which B cells will respond. In response to this selection, the B cells
divide, producing clones that recognize the same epitope.
How does a naive lymphocyte differ from an activated one?
A naive lymphocyte has never "seen" the epitope to which it is programmed to respond.
Activated lymphocytes have encountered the epitope and have received any required
accessory signals.
Name three types of antigen-presenting cells (APC)
Dendritic cells, macrophages, and B cells
Each of the following statements concerning gonorrhea is correct EXCEPT:
A. Infection in men is more frequently symptomatic than in women.
B. The definitive diagnosis can be made by detecting antibodies to Neisseria
gonorrhoeae in the patient's serum.
C. A presumptive diagnosis can be made by finding gram-negative kidney bean
shaped diplococci within neutrophils in a urethral discharge.
D. Anorectal and pharyngeal infections are important sources of the organism.
E. Gonococcal conjunctivitis of the newborn rarely occurs in the US because
silver nitrate or erythromycin is commonly used as prophylaxis.
, B. The definitive diagnosis can be made by detecting antibodies to Neisseria
gonorrhoeae in the patient's serum.
The herpesviruses are able to evade the host's immune response by which
mechanism?
A. Block interferon production
B. Prevent CD8 T-cell killing
C. Block IL-1 and TNF-mediated inflammation
D. Cause genetic change after infection
E. Establish latent infections
E. Establish latent infections
Each of the following statements about HIV is correct EXCEPT:
A. A DNA copy of the HIV genome integrates into host cell DNA.
B. Acyclovir inhibits HIV replication
C. HIV is an enveloped RNA virus
D. The virion contains an RNA-dependent DNA polymerase
B. Acyclovir inhibits HIV replication
Which of the following is a widely used nontreponemal serologic test?
A. RPR
B. Dark field microscopy
C. MHA-TP
D. FTA-ABS
E. TP-PA
A. RPR
Which cell type would NOT be present in a boy born without a thymus?
A. T cell
B. Macrophages
C. NK cell
D. B cell
E. Neutrophils
A. T cell
During a medical check-up for a new insurance policy, a 60 YO grandmother is
found to be positive in the ELISA screening test for antibodies against HIV-1
infection. She has no known risk factors for exposure to the virus. Which of the
following is the mots appropriate next step?
A. Test the patient for Pneumocystis jiroveci infection
B. Immediately begin therapy with azidothymidine
C. Tell the patient that she is likely to develop AIDS
D. Perform the screening test a second time
E. Request that blood culture be performed in a laboratory
D. Perform the screening test a second time
How can a B cell be distinguished from a T cell?
A. T cells mature in the bone marrow
B. Extensive gene recombinations occur in B cells
C. B cells have surface immunoglobulin
D. B cells have a large nucleus-to-cytoplasm ratio
E. B cells have a sheep RBC receptor
