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CHAPTER 16
LYMPHATIC SYSTEM AND IMMUNITY
LEARNING OBJECTIVE 1: Describe the general functions of the lymphatic system.
and
LEARNING OBJECTIVE 2: Identify the locations of the major lymphatic pathways.
Lecture Suggestions and Guidelines
1. Introduce the lymphatic system and its association with the cardiovascular
system.
2. Describe the lymphatic pathways, including a discussion of lymphatic capillaries,
vessels, trunks, and collecting ducts.
3. Discuss the role of lymph nodes.
4. Describe the location and function of the right lymphatic duct and the thoracic
duct.
Application Question(s)
1. Ask students to label a diagram of the human body with the locations of the major
lymphatic trunks and collecting ducts.
Answer: The diagram should include the jugular trunk, subclavian trunk,
bronchomediastinal trunk, intercostals trunk, intestinal trunk, lumbar trunk, right
lymphatic duct, and the thoracic duct.
Critical Thinking Issue(s)
1. Discuss the purpose of tonsils. What causes tonsillitis?
Answer: The tonsils are a form of lymph tissue, which filters bacteria and
destroys them through phagocytosis. Frequently, the streptococcal organisms
cause the tonsils to become infected and irritated. This may lead to a narrowing of
the passageway for swallowing, fever, and leukocytosis. The treatment of choice
is antibiotics. An untreated streptococcal infection is potentially dangerous.
LEARNING OBJECTIVE 3: Describe how tissue fluid and lymph form, and explain
the function of lymph.
and
LEARNING OBJECTIVE 4: Explain how lymphatic circulation is maintained, and
describe the consequence of lymphatic obstruction.
Lecture Suggestions and Guidelines
1. Review the processes of diffusion and filtration.
2. Discuss tissue fluid formation and osmotic pressure.
3. Describe lymph formation and function.
4. Describe the function of flap-like valves in the lymphatic capillary wall.
5. Discuss methods employed to insure lymph movement and flow.
6. Give examples of conditions, which may lead to an obstruction of lymph
movement.
Application Question(s)
1. Apply the information provided by this learning objective to develop a flowchart
depicting the lymphatic pathway.
Answer: The flowchart should include lymphatic capillaries, lymphatic vessels,
lymph nodes, lymphatic trunk, collecting duct, and the subclavian vein.
Critical Thinking Issue(s)
1. Discuss elephantiasis.
Answer: Elephantiasis is a disease of the lymphatic system in which the
lymphatic vessels are blocked by parasitic worms. The blockage will not allow
the lymph to circulate properly, causing severe edema, primarily in the
extremities. Although relatively uncommon, the disease can be debilitating and
painful.
LEARNING OBJECTIVE 5: Describe a lymph node and its major functions.
and
LEARNING OBJECTIVE 6: Describe the location of the major chains of lymph nodes.
Lecture Suggestions and Guidelines
1. Discuss the structure of a lymph node, including the hilum, nodules, and lymph
sinuses.
2. Review the terms afferent and efferent.
3. Describe the tonsils and Peyer’s patches.
4. Discuss the major functions of lymph nodes and give examples of seven major
lymph node locations.
Application Question(s)
1. Provide the following terms to students: trabecula, subcapsule, sinus capsule,
germinal center, nodule, medulla, and hilum. Ask students to sketch a lymph node
and apply these terms to it.
Critical Thinking Issue(s)
1. Under what conditions might lymph nodes be swollen, but not painful?
Answer: Responses should include a discussion of cancer. Some cancers utilize
lymphatic vessels for transportation throughout the body.
LEARNING OBJECTIVE 7: Discuss the functions of the thymus and spleen.
Lecture Suggestions and Guidelines
1. Introduce the general anatomy, physiology, and location of the thymus and
spleen.
2. Briefly describe the role of lymphocytes in providing immunity.
3. Review the role of thymosin.
4. Describe the spleen in terms of red pulp and white pulp, and its association with
macrophages and lymphocytes.
Application Question(s)
1. Compare and contrast the functions of the spleen and thymus.
Answer: Both the spleen and thymus are lymphoid organs. The spleen
synthesizes lymphocytes, the thymus produces hormones which help program the
lymphocytes to perform certain functions. The spleen filters blood, unlike lymph
nodes, which filter lymph. Both spleen and thymus contain reticular connective
tissue and lymphocytes.
Critical Thinking Issue(s)
1. Discuss a condition in which removal of the spleen may be beneficial.
Answer: Lecture on various types of hemolytic anemias. A congenital form, in
which the red blood cells are vulnerable to excessive hemolysis by the spleen, is
one example.
LEARNING OBJECTIVE 8: Distinguish between innate (nonspecific) and adaptive
(specific) defenses, and provide examples of each.
and
LEARNING OBJECTIVE 9: List seven innate body defense mechanisms, and describe
the action of each mechanism.
Lecture Suggestions and Guidelines
1. Describe various examples of nonspecific defense mechanisms. Include a
discussion of species resistance, mechanical barriers, chemical barriers, fever,
inflammation, and phagocytosis.
2. Introduce the concept of specific immunity. More detailed information will be
discussed in meeting subsequent learning objectives.
3. Summarize the major actions that may occur during an inflammation response.
4. Define the terms interferon, pyrogen, and macrophage.
5. Discuss various types of infections.
Application Question(s)
1. Ask students to prepare a chart, which summarizes nonspecific body defenses.
Include specific examples of each type.
Answer: Types of nonspecific defenses include species resistance, mechanical
barriers, chemical barriers, fever, inflammation, and phagocytosis. Specific
examples of each will vary.
Critical Thinking Issue(s)
1. Discuss the nonspecific defense mechanisms, which would be activated and
violated following a situation in which a barefoot child has stepped on a rusty
nail, which pierced the skin.
Answer: Responses will vary, but should employ several nonspecific defense
mechanisms.
LEARNING OBJECTIVE 10: Explain how two major types of lymphocytes are
formed, activated, and how they function in immune mechanisms.
Lecture Suggestions and Guidelines
1. Discuss the origins of lymphocytes and specialization into B cells and T cells.
2. Describe the term antigen and give several examples.
3. Define hapten.
4. Distinguish between cell-mediated immunity and antibody-mediated immunity.
5. Define cytokines.
6. Discuss the general functions of lymphocytes and lymphocyte clones.
7. Describe the process of B cell activation and the polyclonal response.
Application Question(s)
1. Ask students to develop a table which compares T cells and B cells.
Answer: The table should describe differences between humoral and cellmediated immunity, origin of undifferentiated cells, site of differentiation, and
primary locations. T cells can further be subcategorized as helper T cells, killer T
cells, and suppressor T cells.
Critical Thinking Issue(s)
1. Ask students to prepare a short report about the interrelationship between T cells
and AIDS. Which type of T cell provides a prime target for AIDS?
Answer: Discussion should lead to a description of the role of the cluster-ofdifferentiation antigen.
LEARNING OBJECTIVE 11: Name the major types of immunoglobulins, and discuss
their origins and actions.
Lecture Suggestions and Guidelines
1. Introduce the five major types of immunoglobulins. Describe each name,
occurrence, and major function.
2. Describe the role of complement.
3. Discuss the actions of antibodies.
Application Question(s)
1. Provide students with a drawing of each of the five major immunoglobulins. Have
them identify each by name, give the location where each would be found in the
body, and give a description of their biological functions.
Answer: Responses should include a discussion and identification of IgD, IgM,
IgG, IgA, and IgE.
Critical Thinking Issue(s)
1. Ask students to investigate the sequence of complement activation in more detail.
Answer: The sequence of complement fixation involves nine separate proteins.
An antigen-antibody complex activates C1, which creates a complex that activates
C4 and C2, creating a complex which activates C3, creating a complex which
activates C567, creating a complex which activates C89, which will finally result
in the punching of holes in foreign cell membranes.
LEARNING OBJECTIVE 12: Distinguish between primary and secondary immune
responses.
Lecture Suggestions and Guidelines
1. Describe the events which occur when B cells or T cells first encounter an
antigen.
2. Define memory cells.
3. Explain the occurrence of a secondary immune response.
Application Question(s)
1. What sequence of events occurs after a macrophage digests antigen-bearing
agents?
Answer: Students may develop a flowchart of events, including the activation of
helper T cells, T cell interaction with B cells, binding of macrophages to
lymphocytes, and the triggering of other immune defenses.
Critical Thinking Issue(s)
1. Ask students to illustrate the proliferation of activated B cells, which give rise to
plasma cells and memory cells.
Answer: Illustrations will vary.
LEARNING OBJECTIVE 13: Distinguish between active and passive immunity.
Lecture Suggestions and Guidelines
1. Discuss active immunity. Distinguish between naturally-acquired and artificiallyacquired active immunity. Give examples of each.
2. Describe passive immunity. Distinguish between naturally-acquired and
artificially-acquired passive immunity. Give examples of each.
3. Define the term vaccine.
4. Discuss the competence of the immune system with advancing age.
Application Question(s)
1. What are some examples of active and passive naturally acquired immunity?
Answer: Examples of naturally acquired active immunity might be infection
caused by a pathogenic organism. Antibodies crossing the placenta from mother
to fetus would be an example of naturally acquired passive immunity.
Critical Thinking Issue(s)
1. Discuss the advantages of receiving a vaccine.
Answer: Responses will probably include a discussion of protection from disease,
i.e., we would not be required to suffer through the signs and symptoms activated
by a primary response. Also, booster shots facilitate antibody production and
memory.
LEARNING OBJECTIVE 14: Explain how allergic reactions, tissue rejection
reactions, and autoimmunity arise from immune mechanisms.
Lecture Suggestions and Guidelines
1. Describe allergic or hypersensitivity reactions.
2. Define a delayed-action allergy.
3. Discuss anaphylactic shock.
4. Discuss tissue rejection reactions and their similarity to cell-mediated responses.
5. Describe four major types of grafts. Give examples of each.
6. Define autoimmunity and describe a variety of autoimmune disorders.
Application Question(s)
1. What is graft-versus-host disease?
Answer: Graft-versus-host disease is a common concern during bone marrow
transplantation. The recipient’s cells are sometimes mistaken as foreign, and are
attacked by the donor’s lymphocytes. This disease is often fatal, causing
remarkable changes in the liver, intestine, and skin.
Critical Thinking Issue(s)
1. Ask students to research a major autoimmune disease. The report should include a
definition of the disease, the antigen involved, the manifestations, signs and
symptoms, course, outcome, prognosis, and survival rate of the disease.
Answer: Some examples include autoimmune hemolytic anemia, myasthenia
gravis, rheumatic heart disease, systemic lupus erythematosus, and rheumatoid
arthritis.
LEARNING OBJECTIVE 15: Describe life-span changes in immunity.
Lecture Suggestions and Guidelines
1. Describe the general changes in the immune system.
2. Discuss the effects of aging on the declining strength of the immune response.
3. Identify the shift in various antibody classes.
Application Question(s)
1. Ask students to identify the changes in the immune system that occur with AIDS.
Answer: Discussion should include opportunism, symptoms, structure of the
virus, effects on helper T-cells, etc.
Critical Thinking Issue(s)
1. Compare and contrast various methods being researched to combat AIDS.
Answer: Responses may include an analysis of various drugs and a discussion of
receptor molecules.
RELATED DISEASES OF HOMEOSTATIC INSTABILITY
1. Infectious Mononucleosis—A viral infection caused by the Epstein-Barr virus. It
is commonly referred to as “mono,” “the kissing disease,” or “the college
disease.” An increased appearance of atypical lymphocytes is present. Signs and
symptoms include fever, fatigue, sore throat, and swollen lymph nodes. The major
treatment is bed rest.
2. Hodgkin’s Disease—The most common type of lymphoma. It is malignant in
nature and appears to be of viral or infectious origin. Symptoms include painless
lymph nodes, nonspecific malaise, fever, weight loss, itching of skin, and the
presence of large, atypical macrophages. Remission is common.
3. Anaphylaxis—A hypersensitivity reaction influenced by IgE antibodies. The
reaction may be localized (rash, wheals, or hives) or systemic. The systemic
version is more severe and may include a drop in blood pressure and an inability
to breathe.
SUGGESTIONS FOR ADDITIONAL READING
Baltimore, David. January 26, 1995. Lessons from people with nonprogressive HIV
infection. New England Journal of Medicine, vol. 332. A small percentage of people
infected with HIV for more than a decade have not become ill—why? This issue of
the journal contains several articles on long-term survivors of AIDS.
Cohen, Jon. July 1, 2005. Can we selectively shut off immune responses? Science,
2005:97.
Diamond, Jared. September 1992. The mysterious origin of AIDS. Natural History. Did
the AIDS epidemic begin because of a single mutation in a virus or as a terrible side
effect of vaccine research decades ago? Or has AIDS been around for a long time, but
simply gone unnoticed among the infections common in some societies?
Fields, Bernard N. May 12, 1994. AIDS: Time to turn to basic science. Nature, vol. 369.
Understanding the interactions between HIV and the human immune system will help
us develop treatments and a vaccine.
Johnson, Howard M. et al. May 1994. How interferons fight disease. Scientific American.
They are not the cure-all researchers once hoped they would be, but they are
providing therapy for a variety of infectious illnesses and for some cancers.
Landry, Donald W. February 1997. Immunotherapy for Cocaine Addiction. Scientific
American.
Lewis, Ricki. July 1991. Joint attack: Arthritis. FDA Consumer. Rheumatoid arthritis is
an autoimmune disorder.
Lowenstein, Jerold M. June 1993. The transplant gap. Discover. We humans don’t supply
enough organs for transplant. Can animals solve our problem?
Marzuola, Carol. November 9, 2002. First Line of Defense–Hints of Primitive antibodies.
Science News.
McIntosh, K. And S. K. Burchett. March 30, 1995. Clearance of HIV-lessons from
newborns. New England Journal of Medicine, vol. 332. At first, researchers thought
that babies with HIV infection who became free of the virus reflected laboratory
errors—that is, they had never really been infected. They were wrong. This is the first
official report of such a child—his recovery may help us beat AIDS.
Murray, Joseph E. June 5, 1992. Human organ transplantation: Background and
consequences. Science, vol. 256. An extensive and fascinating review of the
development of transplantation medicine.
Nowak, Rachel. December 17, 1993. “Bubble boy” paradox resolved. Science, vol. 262.
SCID is sometimes caused by defective cytokine receptors.
Old, Lloyd J. September 1996. Immunotherapy for Cancer. Scientific American.
Sanfilippo, Fred. September 22, 1994. HLA matching in renal transplantation. New
England Journal of Medicine, vol. 331. The closer the HLA match, the more likely a
kidney transplant is to succeed.
Short, Nicholas. February 1995. A fight to the death. Nature Medicine, vol. 1. HIV
reproduces so rapidly that it is only a matter of time until it overwhelms the human
immune system.
Wain-Hobson, Simon. January 12, 1995. Virological mayhem. Nature, vol. 373. HIV
infection spirals out of control much sooner than we had thought.
Winter, Greg and Cesar Milstein. January 24, 1991. Man-made antibodies. Nature, vol.
349. Genetic engineering can provide antibodies not seen in nature.