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Inflammation and Infection 57
Figure 4-13 Helminth.
Malaria, which is spread by mosquitoes, is the
most prevalent protozoan infection worldwide but is
uncommon in the United States. The protozoa caus
ing malaria live in and destroy the red blood cell of
the host. Giardiasis (gee-ar-DIE-a-sis) is an intestinal
infection caused by drinking water infected with the
Giardia lamblia protozoan; it is treated with antibiotic
therapy.
Helminths
Helminths (Figure 4-13) are any of the roundworms or
flatworms. Helminth infestation is common worldwide
but not as common in the United States. Pinworms
and tapeworms are the most common helminths. Pin
worms cause anal itching but do not cause serious
illness. Tapeworms, acquired by eating uncooked or
inadequately cooked meat, can cause intestinal disease
in humans.
Testing for Infection
Symptoms of infection in an individual can include
fever, tachycardia (TACH-ee-KAR-dee-ah; tachy 5
rapid, cardia 5 heart rate), and malaise (general ill
feeling). Often, blood studies will reveal leukocytosis
(leuko 5 white, cyto 5 cell, osis 5 condition), or an
Figure 4-14 Bacterial culture.
increase in the white cell count, and blood from an indi
vidual with septicemia (SEP-tih-SEE-me-ah) will reveal
the presence of the pathogen in the blood. Infection in
the meninges, or meningitis, can show the presence of
pathogens in the individual’s spinal fluid.
A culture is the process of growing pathogenic
cells on or in a gelatin-like substance called media
that pathogenic organisms use for food (Figure 4-14).
Media can be made of different nutrient agars of which
a common one is sheep’s blood agar. Laboratory studies
of how the microorganism uses this food assist in the
determination of the type of pathogen.
A culture is the most definitive test for organisms
in a lesion or wound. Cultures are most commonly used
for bacteria identification but can also identify viral and
fungal infections. Most specimens are obtained from
the throat, urine, sputum, purulent wound lesions,
feces, blood, and spinal fluid.
After identification of the pathogen, a sensi
tivity test is used to identify the type of treatment
needed. The combined test for these is called a
culture and sensitivity test. During a sensitivity test,
the microorganisms are grown on the entire surface of
the agar plate. An antibiotic-permeated disk or strip is
placed on the agar plate to determine if the antibiotic
will kill the organism. The larger the kill zone, the
more effective that antibiotic is at killing the organ
ism. Use of the antibiotic-permeated strip, known as
the epsilometer test (Etest
®
), not only shows the kill
zone but also uses graduated markings to indicate the
concentration of antibiotic needed to kill the organ
ism (Figure 4-15).
Specific antigen-antibody reactive tests can be used
to determine the presence of pathogens. For example,
a rapid diagnosis of strep throat can be made by testing
for the presence of an antigen in a throat specimen. The
Streptococcus antigen will clot or clump when mixed
with a laboratory Streptococcus antibody.
58 Chapter 4
Figure 4-15 Sensitivity test. (A) Disk method. (B) Etest®.
Bacterial, rickettsial, and some other pathogenic
infections can be determined by serologic testing, which
uses the individual’s blood serum to test for antibodies
against the pathogen.
Skin testing also uses antibody presence to deter
mine exposure to pathogens. Tuberculosis (TB) skin
testing (also called the Mantoux test) is one of the most
common skin tests and involves the intradermal (under
the skin) injection of tuberculin bacteria particles (anti
gen; Figure 4-16). If an individual has been exposed
to TB and has developed the TB antibody, this anti
body will attack the antigen and cause an induration
(IN-dur-RAY-shun; hardened tissue), displaying a pos
itive skin test (Figure 4-17).
Figure 4-16 Tuberculosis (TB) skin test. Figure 4-17 Positive skin test.
Courtesy of Mark L. Kuss Courtesy of Mark L. Kuss
Testing for MRSA includes culture and sensitivity
of infected body tissues or nasal secretions. Treatment
is often delayed because completion of this test takes a
minimum of 48 hours. The Xpert MRSA® uses DNA-
type technology to test for the drug-resistant strain.
This test can determine the presence of MRSA within
an hour, but the cost is often prohibitive, especially for
smaller health care facilities.
A positive skin test and serology testing might not
indicate current infection or the degree of infection.
These tests are only a few of the many laboratory tests
used in diagnosing pathogenic infections and indicate
only that the individual has been exposed to the patho
gen and has developed antibodies.
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Inflammation and Infection 59
Summary
T
he body responds to the invasions of pathogens by using its defense mechanisms. Inflammation is a natural protective
mechanism that occurs when physical barriers are broken and the invader penetrates the tissues. The inflammatory
process consists of a series of events that eventually, if functioning properly, destroy the invading pathogen.
When this system of protection fails, infection can occur. Infections are caused by a variety of organisms, most
commonly by bacteria and viruses. They are diagnosed and treated in a variety of ways. Several kinds of laboratory
tests can be used to identify the organism and determine the appropriate therapy.
Review Questions
Short Answer
1. What are the three defense mechanisms of the body? (Describe them.)
2. What are the steps in the inflammatory process?
3. How do inflammatory exudates and inflammatory lesions differ?
4. What are the five cardinal signs of inflammation?
5. What is the difference between a keloid and an adhesion?
6. Compare and contrast some microorganisms that produce infection in humans.
7. What type of testing is used to identify the organism causing an infection?
Fill in the Blanks
8. Cellular proliferation can be grouped into the three categories of,, and
9. The body’s two main methods of repair involve and
10. Primary union is also called
11. The process of secondary union involves a larger degree of and more to resolve it
than primary union requires.
12. The greatest impediments to wound healing are and
60 Chapter 4
Case Studies
■ Ms. Jannicet is an 85-year-old resident in a local long-term care facility. She is very thin and frail and, except
for meals, stays in bed most of the day. This puts her at risk of developing pressure ulcers. On what areas of her
body would she most likely develop pressure ulcers? How can they be prevented? How would you describe a
pressure ulcer? Describe the healing process of a pressure ulcer.
■ Mr. Jordan has a sore throat and frequent cough, so he made an appointment with his physician for an
evaluation. He was diagnosed with an upper respiratory infection. The physician prescribed an antibiotic to be
taken four times a day for 10 days. What are some important points about taking the medication that Mr. Jordan
should know? Although he already has an infection, is good handwashing still important? If so, why?
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Unit
Common Diseases and
Disorders of Body Systems
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5
Immune System
Diseases and
Disorders
Key Terms
Allergen(s) (p. 65)
Allergy (p. 65)
Anaphylaxis (p. 70)
Antigen(s) (p. 65)
Autoimmune (p. 65)
Bronchospasm (p. 69)
Corticosteroid(s) (p. 70)
Cytotoxic (p. 81)
Hemolytic (p. 66)
Hypersensitivity (p. 65)
Immunodeficiency (p. 65)
Isoimmune (p. 65)
Kaposi’s sarcoma (p. 82)
Pneumocystis carinii
pneumonia (p. 82)
Prophylactic (p. 72)
Self-antigen (p. 72)
Status asthmaticus (p. 70)
Streptococcal (p. 72)
Urticaria (p. 67)
Learning Objectives
Upon completion of the chapter, the learner should be able to:
1. Define the terminology common to the immune
5. Identify disorders of the immune system.
system and the disorders of the system.
6. Describe the typical course and management of
2. Discuss the basic anatomy and physiology of the common immune system disorders.
immune system.
7. Describe the effects of aging on the immune
3. Identify the important signs and symptoms system and the common disorders of the system
associated with common immune system
disorders.
associated with aging.
4. Describe the common diagnostics used to determine
the type, cause, or both of an immune system
disorder.
Overview
T
he immune system protects the body through the processes of defense, attack, and removal of pathogens.
The immune system also helps the body by removing aged or dead cells and other debris. Diseases or
disorders of the immune system can range from mild to severe and can affect individuals of any age, race, or
gender. Many of the disorders of the system are extremely debilitating and require long-term therapy. If the
63
immune system is not functioning properly due to disease or other influencing factors, the result may be a
secondary disease of the body resulting from the compromised immune system. ■
Anatomy and Physiology
The immune system is made up of a complex group of
cells and organs found throughout the body. The sys
tem includes primary organs, such as the thymus gland
and the bone marrow, and secondary organs, such as
the lymph nodes, spleen, liver, and tonsils (Figure 5-1).
Lymphocytes, the major cells of the immune system,
arise and develop in the primary organs. The secondary
organs are responsible for filtering foreign substances
and providing the space for antigen reactions.
The cells of the immune system include four types of
leukocytes: polymorphonuclear leukocytes, monocytes,
macrophages, and lymphocytes. The polymorphonu
clear leukocytes (PMNs), also known as granulocytes,
are active in the inflammatory process. Some leukocytes
react when infection threatens the body; others respond
to prevent damage to cells and tissues from an aller
gic reaction. The monocytes and macrophages become
phagocytic in the presence of pathogens and foreign
substances. The lymphocytes are the major players in
the immune response (Table 5-1).
Lymphocytes are formed in the bone marrow.
Those remaining and maturing in the bone marrow
become B lymphocytes. Others migrate and mature in
Tonsils and
adenoids —
the thymus and become T lymphocytes. When mature,
both B and T lymphocytes enter the blood and circulate
and colonize the lymphatic organs, predominately the
spleen and the lymph nodes.
T lymphocytes, or T cells, are responsible for the
cell-mediated response. These cells destroy microor
ganisms that invade the body. These reactions do not
require antibodies produced by the B lymphocytes or
B cells because the T cells have been previously sen
sitized by circulating antigens. Several types of T cells
function to stimulate B cells to produce antibodies,
destroy foreign cells in the body, stop the immune
response, and remember previous exposure to antigens.
B lymphocytes are responsible for humoral immu
nity. Humoral immunity is associated with circulating
antibodies in contrast to cell-mediated immunity. The
B lymphocytes enlarge and divide to become mature
plasma cells. The plasma cells secrete antibodies into
the blood and lymph to protect the body against infec
tions and toxins produced by microorganisms.
There are two types of immune responses in the
body: specific and nonspecific. A specific immune
response is associated with antigens and the antibody
reaction. It is the body’s watch-guard system for foreign
invaders. The antibody response occurs after exposure
to an antigen. Antibodies may neutralize, kill, or cause
clumping of the foreign microorganism. Antibodies
may be assisted by the complement system. This system
is a group of proteins that are formed in the liver and
Lymphatic
vessels —
Bone
marrow
Lymph
nodes
Thymus
Skin
Spleen
Appendix
and Peyer’s
patches
Figure 5-1 Organs of the immune system.
TABLE 5-1 Types and Functions of Leukocytes
Type
Function
Polymorphonuclear leukocytes
Neutrophils Phagocytosis
Eosinophils Allergic response
Basophils Histamine release
Monocytes Become macrophages
(phagocytosis)
Macrophages Phagocytosis
Lymphocytes
T lymphocytes
B lymphocytes
Plasma cells
Cell-mediated immunity
Humoral immunity
Antibody production
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Immune System Diseases and Disorders 65
TABLE 5-2 Types of Immunity
Type of Immunity
Example
Active natural Having the disease (such
immunity as mumps)
Active artificial Receiving a vaccination (such
immunity as MMR)
Passive natural Antibodies produced by the
immunity body itself or received from
maternal-fetus transmission
Passive artificial
immunity
Injection of antibodies
circulate in the serum. The complement system works
with and enhances the work of the antibodies to destroy
the invader.
The nonspecific immune response includes inflam
mation, phagocytosis, physical barriers (the skin and
mucous membranes), and chemical barriers (acids and
other secretions). These immune response defenses
are the body’s first line of protection against foreign
invaders.
There are several ways to classify types of immu
nity, but the most common method is to divide immu
nity into passive and active and then further divide
these types into natural and artificial. Table 5-2 out
lines the types of immunity and gives examples of each.
In addition, some classification systems use the term
natural resistance when describing immunity. Natu
ral resistance is the inherited immunity the individual
may possess due to race, species, or ethnic background.
Some races, species, or particular groups of populations
are naturally resistant to certain diseases, just as some
are more susceptible to certain diseases.
Common Signs and Symptoms
In some cases, a patient’s concern can be considered as
both a symptom and a sign. Some references call this an
objective or observable symptom, whereas others state
that it is also a sign. An example would be a patient
complaining of a runny nose. The runny nose is the
patient’s symptom, and because it is observable to the
physician, it is also a sign.
The common signs and symptoms related to the
various immune system diseases are quite varied,
depending on the organ or organ system affected.
Symptoms common to allergic reactions include local
or systemic inflammatory responses (redness, heat,
swelling, itching) and respiratory symptoms (runny
nose, coughing, sneezing, nasal congestion).
The classic clinical problem with immune defi
ciency disorders is the development of unusual and
severe infections, such as pneumonia, meningitis, or
septicemia, to name just a few. Also, the development
of infections by microorganisms that are not usually
pathogenic (opportunistic infections) might be indic
ative of an immunodeficiency (lack of immunity)
disorder. The common signs and symptoms related to
the various autoimmune (immunity against self) and
isoimmune (immunity against other humans) disor
ders are also varied, depending on the organ or organ
system affected and the invading pathogen. For this
reason, signs and symptoms of these diseases such as
rashes, plaques, and itchy skin patches are identified in
the discussion of the specific disease.
Diagnostic Tests
Determining the cause of an allergic reaction might
be quite difficult. There are hundreds of possible
antigens (allergens) that cause allergic reactions.
Some of the more common allergens are house dust,
pet hair, chocolate, ragweed, cigarette smoke, pollen,
seafood, nickel, plants, paints, dyes, and chemical
cleaners.
The most important test for diagnosing allergies is
the skin test. A skin test may be performed by intra
dermal injection involving injection of a small amount
of the suspected antigen under the skin. A skin patch
test utilizes placing a small antigen-soaked patch placed
against the individual’s skin. Another skin test is a
scratch test in which a small amount of suspected anti
gen is placed in a small scratch. All three types of tests
are used to identify an allergen.
An allergy to the antigen is positive if an inflamma
tory response or wheal occurs at the injection site. The
size of the wheal is usually indicative of the individual’s
sensitivity to the allergen. There are hundreds of aller
gic antigens that may be used in skin testing.
After an antigen has been identified, a desensiti
zation treatment may be attempted. Desensitization
requires the injection of an increasing amount of aller
gen over a long time, with the goal of desensitizing the
body to the allergen. Other treatments include anti
histamine medications and avoiding exposure to the
allergen.
Hypersensitivity reactions to transfused blood
cells are usually identified by a blood count indicat
ing low levels of red cells, white cells, and platelets.
66 Chapter 5
Healthy Highlight
The Importance
of Sleep to the
Immune System
T
he immune system is a complex system because its cells and diseases are so different
and unique. Good sleep is important for many body functions, but in particular, it
is important for proper immune system function. Poor sleep can adversely affect the
immune system in fighting off infectious diseases. People who do not get enough sleep
are more susceptible to cold viruses and other bacterial or viral diseases. Recommenda
tions for optimal sleep are 7 to 8 hours for adults, 9 to 10 hours for teens, and 10 to
12 or more for primary school-aged children.
Antibodies can form against all these blood elements,
leading to anemia, leukopenia, and thrombocytopenia,
respectively.
A Coombs test will indicate the formation of anti
bodies on the red blood cell. This test can be used to
determine blood type and diagnose certain hemolytic
(HE-moh-LIT-ick; hemo = blood, lytic = destroying)
anemias. A Coombs test can also indicate the presence
of maternal antibodies against the fetal blood type, as
occurs in erythroblastosis fetalis.
Autoimmune disorders can be diagnosed using
blood tests that measure for specific diseases. For exam
ple, individuals with systemic lupus erythematosus
will have a positive antinuclear antibody (ANA) test.
Rheumatoid factor (RF) in the blood is often indica
tive of rheumatoid arthritis. Another test for rheuma
toid arthritis is the presence of anticyclic citrullinated
peptide (anti-CCP) antibodies. This test is also used to
predict those who will have more severe effects of the
disease.
Immunodeficiency disorders are usually diagnosed
by blood testing that reveals low white cell counts, spe
cifically B and T lymphocytes. The presence of an anti
body in the blood against a causative pathogen can also
be used. Finding an antibody against the human immu
nodeficiency virus (HIV) is indicative of exposure to
acquired immunodeficiency syndrome (AIDS). Genetic
testing may also be done to determine the likelihood of
someone getting an immune system disorder such as
rheumatoid arthritis.
Common Diseases of
the Immune System
Diseases of the immune system can be divided into two
main groups: hypersensitivity disorders and immune
deficiency disorders. Several specific diseases are within
each grouping. Each of these has some unique problems
associated with the disease, but some of the signs and
symptoms may be quite similar.
Pharmacology
Highlight
Common Drugs for Immune Disorders
Category Examples of Medications
Antihistamines
Drugs used to reduce the
symptoms from allergies
Carbinoxamine or levocabastine (prescription drugs);
fexofenadine, cetirizine, or loratadine (over-the-
counter drugs)
Anti-inflammatories
Drugs used to reduce
inflammation
Hydrocortisone, beclomethasone, or amcinonide
(steroids); aspirin or ibuprofen (nonsteroidal)
Antipyretics/Analgesics
Drugs used to reduce fever
and pain
Acetaminophen, aspirin, ibuprofen, or naproxen
(continued )
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