Chapter 18
4. Which statement is incorrect?
a. The most abundant immunoglobulins are IgG and IgM
b. IgG antibodies are involved in specifi c immune responses
against bacteria and viruses in the extracellular fl
c. IgM antibodies are primarily involved in immune
defense mechanisms found in the surface or lining of the
gastrointestinal, respiratory, and genitourinary tracts.
d. All antibodies of a given class have an Fc portion that is
identical in amino acid sequence.
e. Antibodies can exist at the surface of a B cell, or be
circulating freely in the blood.
5. Antibiotics are useful for treating illnesses caused by viruses.
6. Chronic infl ammatory diseases may occur even in the absence
of any infection.
7. All T cells are derived from lymphocytes, but not all
lymphocytes are T cells.
8. Edema, which occurs during infl ammation, has important
adaptive value in helping defend against infection or injury.
9. Bone marrow and the thymus gland are examples of secondary
lymphoid organs.
Chapter 18 Quantitative and Thought Questions
(Answers appear in Appendix A.)
1. If an individual failed to develop a thymus because of a genetic
defect, what would happen to the immune responses mediated
by antibodies and those mediated by cytotoxic T cells?
2. What abnormalities would a person with a neutrophil defi ciency
display? A person with a monocyte defi ciency?
3. An experimental animal is given a drug that blocks
phagocytosis. Will this drug prevent the animal’s immune
system from killing foreign cells via the complement system?
4. If the Fc portion of a patient’s antibodies is abnormal, what
effects could this have on antibody-mediated responses?
5. Would you predict that patients with AIDS would develop fever
in response to an infection? Explain.
Chapter 18 Answers to Physiological Inquiries
Figure 18–6
Many molecules in the body act this way.
For example, somatostatin acts locally in the stomach to
control acid production (paracrine) and is secreted into the
hypothalamo-pituitary portal veins to control growth hormone
secretion (endocrine). Testosterone acts locally within the
testes (paracrine) and reaches other targets through the blood
Figure 18–7
Vasodilation and increased protein permeability
of the microcirculation both contribute to an increase in the
rate of fi ltration of fl uid from the plasma into the interstitial
space. Because lymph vessels are the main route by which
fl uid and protein are returned from the interstitial space to
the circulatory system (see Figure 12–47), these changes will
lead to increased fl ow of lymph. As that fl
uid fl ows through
the lymph nodes, lymphocytes are exposed to antigens from
the invading pathogen, thus activating the specifi c immune
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