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U N I T 4
Infection and Immunity
R E V I EW E X E R C I S E S
1.
A 32-year-old man presents in the allergy clinic with
complaints of allergic rhinitis or hay fever. His major
complaints are those of nasal pruritus (itching), nasal
congestion with profuse watery drainage, sneezing,
and eye irritation. The physical examination reveals
edematous and inflamed nasal mucosa and redness
of the ocular conjunctiva. He relates that this
happens every fall during “ragweed season.”
A.
Explain the immunologic mechanisms that are
responsible for this man’s symptoms.
B.
What type of diagnostic test might be used?
C.
What type(s) of treatment might be used to
relieve his symptoms?
2.
Persons with intestinal parasites and those
with allergies may both have elevated levels of
eosinophils in their blood.
A.
Explain.
3.
A 20-year-old woman has been diagnosed with
IgA deficiency. She has been plagued with frequent
bouts of bronchitis and sinus infections.
A.
Why are these types of infections particularly
prominent in persons with an IgA deficiency?
B.
She has been told that she needs to be aware
that she could have a severe reaction when given
unwashed blood transfusions. Explain.
4.
Persons with impaired cellular immunity may not
respond to the tuberculin test, even when infected
with
Mycobacterium tuberculosis.
A.
Explain.
5.
A 29-year-old woman presents to the clinic for
her initial obstetric visit about 10 weeks into her
pregnancy.
A.
This woman is in a monogamous relationship.
Should an HIV test be a part of her initial blood
work? Why?
B.
The woman’s HIV test comes back positive.
What should be done to decrease the risk of
transmitting HIV to her child?
C.
The infant is born, and its initial antibody
test is positive. Does this mean the infant is
infected? How is the diagnosis of HIV infection
in a child younger than 18 months made, and
why is this different than the diagnosis for
adults?
6.
A 40-year-old man presents to the clinic very
short of breath, and after a radiograph and an
examination, he is diagnosed with PCP. His
provider does an HIV test, which is positive. Upon
further testing, the man’s CD4
+
cell count is found
to be 100 cells/
μ
L and his viral load is 250,000
copies/mL.
SUMMARY CONCEPTS
■■
Immunodeficiency is an absolute or partial loss
of the normal immune response, which places
a person at increased risk for development of
infections or malignant complications. It can be
classified as primary (i.e., congenital or inherited)
or secondary (i.e., due to another disease or
condition).
■■
Immunodeficiency can affect the humoral or
cellular components of the adaptive immune
system. Defects in humoral immunity increase
the risk of recurrent pyogenic infections but have
less effect on the defense against intracellular
bacteria (mycobacteria), fungi, protozoa, and
viruses (except for the enteroviruses that cause
gastrointestinal infections). Defects in cellular
immunity increase the risk of developing fungal,
protozoan, viral, and intracellular bacterial
infections, and malignant cell proliferation.
■■
Acquired immunodeficiency syndrome
(AIDS), the most common type of secondary
immunodeficiency, is caused by infection with
the human immunodeficiency virus (HIV), a
retrovirus that infects the body’s CD4
+
T cells
and macrophages. Destruction of CD4
+
cells
constitutes an attack on the entire immune
system because this subset of lymphocytes exerts
critical regulatory and effector functions that
involve both humoral and cellular immunity.
■■
The clinical course of HIV infection can be divided
into three phases: a primary phase that occurs
shortly after infection and is usually manifested
by mononucleosis-like symptoms, a latency
phase that may last for years, and an overt
AIDS phase that is characterized by a marked
decrease in CD4
+
T cells and the development of
opportunistic infections, malignancies, wasting
syndrome, and metabolic disorders.There is no
cure for AIDS.Treatment largely involves the use
of drugs that interrupt the replication of HIV and
prevention or treatment of complications such as
opportunistic infections.
■■
Women who are infected with HIV may
transmit the virus to their offspring in utero,
during labor and delivery, or through breast
milk. Diagnosis of HIV infection in children
born to HIV-infected mothers is complicated
by the presence of maternal HIV antibody,
which crosses the placenta to the fetus. This
antibody usually disappears within 18 months
in uninfected children.
