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Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 53
Test Yourself Questions
1. Which of the following is not an example of a barrier defense in animals?
a. skin
b. secretions from skin glands
c. exoskeleton
d. mucus
e. antibodies
Answer: e. Antibodies do not deny pathogens access to an animal's tissue but play a role in destroying
pathogens that have invaded the animal's body.
2. The leukocytes that are found in mucosal surfaces and play a role in defending the body against parasitic
infections are
a. neutrophils.
b. eosinophils.
c. basophils.
d. monocytes.
e. NK cells.
Answer: b. Eosinophils are leukocytes that are found in the mucousal surfaces and play a role in defending the
body against parasitic infections.
3. The vascular changes of inflammation
a. lead to an increase in bacterial cells at the injury site.
b. decrease the number of leukocytes at the injury site.
c. allow plasma proteins to move easily from the bloodstream to the injury site.
d. increase the number of antibodies at the injury site.
e. activate lymphocytes.
Answer: c. The vascular changes of inflammation allow plasma proteins to move easily from the bloodstream to
the injury site.
4. Which of the following statements is correct regarding specific immunity?
a. Specific immunity only requires the presence of helper T cells to function properly.
b. Specific immunity does not require exposure to a foreign substance.
c. Specific immunity is triggered by contact with a particular antigen.
d. Specific immunity includes inflammation.
e. All of the above are correct.
Answer: c. Specific immunity is triggered by contact with a particular antigen.
5. Memory B cells are
a. cloned lymphocytes that are active in subsequent infections.
b. cloned lymphocytes that are active during a primary infection.
c. NK cells that recognize cancer cells and destroy them.
d. cells that produce antibodies.
e. macrophages that have recognized self antigens.
Answer: a. Memory B cells are cloned lymphocytes that are active in subsequent infections.
6. The immunoglobulin that is passed from mother to fetus across the placenta is
a. IgA.
b. IgD.
c. IgE.
d. IgG.
e. IgM.
Answer: d. The immunoglobulin that is passed from mother to fetus across the placenta is IgG.
7. The region of an antibody that serves as the antigen binding site is
a. the constant region.
b. the variable region.
c. the heavy chain.
d. the light chain.
e. the hinge point.
Answer: b. The region of an antibody that serves as the antigen-binding site is the variable region.
8. A major difference between the activation of B cells and T cells is that
a. T cells must interact with antigens bound to cell membranes.
b. B cells only interact with free antigens.
c. B cells are not regulated by helper T cells.
d. T cells produce antibodies.
e. none of the above.
Answer: a. A major difference between the activation of B cells and T cells is that T cells must interact with
antigens bound to cell membranes.
9. Cells that process foreign proteins and complex them with their MHC proteins are called
a. cytotoxic T cells.
b. plasma cells.
c. NK cells.
d. antigen presenting cells.
e. helper T cells.
Answer: d. Cells that process foreign proteins and incorporate them into their MHC proteins are called antigenpresenting cells.
10. HIV causes immune deficiency because the virus
a. destroys all the cytotoxic T cells.
b. preferentially destroys helper T cells that regulate the immune system.
c. directly inactivates plasma cells.
d. causes mutations that lead to autoimmune diseases.
e. all of the above.
Answer: b. HIV causes immune deficiency because the virus preferentially destroys helper T cells that regulate
the immune system.
Conceptual Questions
1.
Distinguish between nonspecific immunity and specific immunity.
Answer: Nonspecific immunity is present at birth and is found in all animals. These defenses recognize general
features of pathogens and include external barriers such as the skin, and internal defenses involving
phagocytes and other cells. Specific immunity develops after an animal has been exposed to a particular
antigen. The responses include humoral and cell-mediated defenses. Specific immunity appears to be largely
restricted to vertebrates.
2.
Explain the function of cytotoxic T cells.
Answer: Cytotoxic T cells are “attack” cells that are responsible for cell-mediated immunity. Once activated, they
travel to the location of their targets, bind to the targets by combining with an antigen on them, and directly kill
the targets via secreted chemicals.
3.
Describe the basic structure of an immunoglobulin.
Answer: Each immunoglobulin molecule is Y shaped and composed of four interlinked polypeptide chains: two
long heavy chains and two short light chains. The chains within the Y have complex loop-like structures due to
disulfide bonds within and between the chains.
Experimental Questions
1. What features of termite physiology and/or behavior reduce the chance that an infection will spread
throughout the colony?
Answer: Termites produce and line their nests with antimicrobial secretions that reduce the probability
that an infection can spread. Termites also practice social grooming that removes foreign objects and
possible pathogens from nest mates. Sick or dead termites are also removed from the nest, thus
decreasing the likelihood of disease transmission.
2. What hypothesis was tested by Traniello and colleagues?
Answer: The researchers tested the hypothesis that social interaction among termites promotes disease
resistance—that termites that had contact with nest mates that had previously been exposed to a pathogen
were subsequently less likely to become infected with that pathogen than termites that lacked prior contact with
nest mates. The researchers regarded this as social immunity.
3. How did the researchers test this hypothesis, and what were the results of the study?
Answer: The researchers formed two groups of termites. The experimental group was exposed to a
microbial pathogen, whereas the control group was not. After 1 week, the control group was divided into
two groups. One control subgroup was introduced to the group of termites previously exposed to the
pathogen, whereas the other control subgroup was kept isolated from the exposed termites. Finally, the
researchers challenged both groups with a lethal concentration of the same microbial pathogen. The
researchers then evaluated the effect of social interaction on survival. The results indicated that the
termites that previously had been introduced to the exposed termites were had higher survival rates
compared to the control group that was not introduced to exposed termites. The researchers concluded
that the interaction with the exposed termites allowed the control termites to acquire immunity to the
microbial pathogen.
Collaborative Questions
1. Discuss three types of pathogens that affect the health of animals.
Answer:
Bacteria: These organisms can either damage tissues directly or release into the bloodstream toxins that can
disrupt functions in other parts of the body. Bacteria are responsible for many of the diseases in humans,
including strep throat, food poisoning, Lyme disease, and pneumonia. These organisms can gain entry through
direct contact with open wounds, through the respiratory system, or through ingestion of food or water.
Viruses: These pathogens are nucleic acids enclosed within a protein coat and are much smaller than
bacteria. They must infect a host cell and commandeer its cellular machinery and energy sources to
make more viruses. Like bacteria, viruses cause many common human diseases, including influenza,
HIV, herpes, and the common cold.
Parasites: These are muticellular eukaryotic organisms such as fungi, protozoa, and some worms. These
organisms can damage tissue and extract nutrients from the host organism. Among the many parasitic diseases
that affect humans are malaria, roundworms, and tapeworms.
2. Describe the major difference between invertebrate and vertebrate immune systems.
Answer: Only vertebrates possess a clearly defined specific (acquired) immunity, although recent
research suggests that some invertebrates may have at least a rudimentary form of specific immunity.