Download Suggested Answers for Case Study, Chapter 16, Mechanisms of

Suggested Answers for Case Study, Porth
Chapter 16, Mechanisms of Infectious Disease
1.
Novel infectious diseases are becoming increasingly prevalent in the Western
hemisphere owing to an expanding global market and international travel.
Modes of transmission include birds, mammals, and insects. West Nile virus is
a vector-borne illness transmitted by mosquitoes.
2.
Antibody titers (or levels) indicate the presence of infection. Certain titers are
elevated during the acute phase of a specific illness and tend to decline during
convalescence.
3.
When Jason was feeling at his worst, he was experiencing the acute phase of
the illness. At this time, there is rapid proliferation and spread of the pathogen
within the body. Toxic byproducts of microbial metabolism and cell lysis
contribute to the specific signs and symptoms of the invading pathogen. The
host’s immune response generates inflammation and tissue damage, further
adding to the clinical presentation.
4.
Viruses have either a single DNA or RNA strand. In order to replicate, they
require the genetic material of a host; they cannot replicate outside of a living
cell. Once in the host cell, they may replicate and migrate from the cell
through “budding” or through cellular lysis. Alternatively, they may lie in a
state of latency to create disease at a later time or alter the genetic material of
the host cell to create malignant transformation.
Suggested Answers for Case Study, Porth
Chapter 17, Innate and Adaptive Immunity
1.
Macrophages are a component of innate immunity and are responsible for the
phagocytosis of microbes and processing of antigen. When working with T
lymphocytes, macrophages can act as antigen-presenting cells. After ingesting
the microbe, digestive enzymes break down antigen into small peptides and
combine it with class II MHC. These complexes are presented on the cell
membrane surface to CD4+ helper T cells, which recognize the antigen–MHC
II complex by means of a T-cell receptor.
2.
Type I interferons are produced by macrophages and fibroblasts. They inhibit
viral replication and allow a virally infected cell to be recognized by
lymphocytes. IFNs are also responsible for triggering uninfected cells to
produce antiviral proteins to inhibit viral synthesis and spread.
3.
Antibodies contribute to the agglutination of microbes to prevent their spread,
facilitate phagocytosis, and encourage their destruction. They have the ability
to neutralize bacterial toxins and inhibit the ability of viruses to invade host
cells. Antibodies also contribute to the activation of complement and assist in
the adherence of antigen to immune cells.
Suggested Answers for Case Study, Porth
Chapter 18, Inflammation, Tissue Repair, and Wound Healing
1.
Carlton’s signs are typical of acute inflammation. Local vasodilation creates
erythema and warmth. The edema is a result of increased vessel permeability
and migration of exudate into the surrounding tissue. The engorgement of
fluid at the area of injury contributes to the sensation of pain.
Visceral inflammation has a slightly different presentation: heat is less likely
to occur because core temperature is preserved at a homeostatic level, and pain
becomes apparent only when stretch receptors on the surfaces of viscera are
stimulated.
2.
In an acute response, leukocytosis occurs to increase the number of circulating
white blood cells to support the immune response. The movement of white
blood cells to the site of injury occurs as a result of chemotaxis. Margination
and emigration are the events that describe the movement of circulating
leukocytes from the blood to the injured tissue; local blood stasis allows
leukocytes to move to the perimeter of vessels and pass (or emigrate) through
capillary walls. Neutrophils arrive early to phagocytize microbes and cellular
debris. Monocytes travel in the blood and migrate to injured tissue, where they
become macrophages. These cells are capable of engulfing greater quantities
of foreign material and are able to move to the lymphatic system, where they
prime specific immunity.
3.
Although the components of nutritional intake are valuable to all stages of
wound healing, some have more specific qualities. Both vitamin A and C
assist collagen synthesis, but vitamin C has a direct influence on collagen
assembly and the removal of byproducts that result from collagen
manufacturing. A deficiency in vitamin C would therefore affect the onset of
the proliferation stage and the effectiveness of the remodeling phase, in which
collagen production and lay-down is critical. Vitamin A stimulates capillary
growth and epithelialization. A deficiency in vitamin A would hinder
angiogenesis in the inflammatory phase of wound healing and epithelialization
in the latter component of the proliferation phase.
Suggested Answers for Case Study, Porth
Chapter 19, Disorders of the Immune Response
1.
Ahmed demonstrated a type I, IgE-mediated hypersensitivity reaction as
indicated by his rhinoconjunctivitis and asthmatic symptoms. The rapid onset
of his respiratory symptoms shortly after putting on the gloves is also typical
of the type I response. Latex allergy can also be attributed to a type IV, T-cellmediated response that presents with dermatologic signs and symptoms that
are more delayed in their onset.
2.
In a type I hypersensitivity disorder, TH2 cells differentiate in response to an
allergen and in turn release IL-3, IL-4, and IL-5. IL-3 and IL-5 recruit and
activate eosinophils, whereas IL-4 stimulates the differentiation of B cells into
IgE-producing plasma cells. The IgE antibodies in turn sensitize mast cells,
which subsequently undergo degranulation when exposed to the allergen. Mast
cells produce vasodilation and smooth muscle spasm. Both mast cells and
eosinophils contribute to the mucosal edema, secretion, and bronchospasm
seen in type I hypersensitivity responses.
3.
The latex proteins responsible for allergic reactions bind readily with the
cornstarch used to coat gloves. In any environment in which gloves are
frequently changed, the cornstarch becomes airborne and liberates aerosolized
latex. A susceptible individual can react to the airborne proteins without
having had contact with the latex material itself.
The proteins responsible for latex allergy reactions have a similar structure to
the proteins found in bananas, avocado, kiwis, tomatoes, and chestnuts. Those
with latex allergy often show cross-sensitivity to these foods.
Suggested Answers for Case Study, Porth
Chapter 20, Acquired Immunodeficiency Syndrome
1.
A number of factors increase the risk for HIV transmission from mother to
infant. A mother who exhibits a low CD4+ count or high viral load during
pregnancy increases the risk for transmitting the disease to the unborn child.
Delayed delivery after rupture of the amniotic sac is another factor that puts
the fetus at risk. Transmission can occur in utero, during delivery, or with
breast-feeding.
2.
HAART refers to highly active antiretroviral therapy. The treatment protocol
involves the administration of two or three antiretroviral medications that
collectively destroy the HIV at various stages of replication. The aim of the
therapy is to reduce the presence of HIV RNA to an undetectable level while
increasing CD4+ cell counts. Zidovudine is a particularly effective
antiretroviral medication to be administered to the pregnant woman because it
greatly reduces the risk for perinatal transmission to the fetus. Some
antiretrovirals, however, are teratogenic and should not be administered to the
mother during the first trimester.
3.
An opportunistic infection occurs when otherwise benign or common
microorganisms cause disease in a compromised host. Individuals with HIV
are prone to opportunistic infection because of CD4+ deficiency. The level of
CD4+ cells directly correlates with the risk for developing an opportunistic
infection. Viral load is another risk factor, and higher HIV RNA levels
predispose the individual to opportunistic illness.