800
UNIT 4
Maintenance of the Body
Related Clinical Terms
Congenital thymic aplasia
An immune deficiency disease in which
the thymus fails to develop. Affected individuals have no T cells,
hence little or no immune protection; fetal thymic and bone
marrow transplants have been helpful in some cases.
Eczema
(ek
9
zĕ-mah) A clinical term for several conditions that
cause “weeping” skin lesions and intense itching. One common
cause,
atopic dermatitis
, has a strong familial predisposition, has
features of immediate hypersensitivity, and usually begins in the
first five years of life. Recent research suggests the underlying
defect may be increased leakiness of the skin.
Hashimoto’s thyroiditis
An autoimmune disease in which both
B and T lymphocytes attack the thyroid gland. It is the most
common cause of hypothyroidism, affecting mostly middle-
aged and elderly women. Genetic factors associated with this
autoimmune disease (certain MHC variants) make individuals
susceptible to environmental triggers (possibly iodine,
irradiation, or trauma).
Immunization
±e process of rendering a subject immune (by
vaccination or injecting antiserum).
Immunology
±e study of immunity.
Immunopathology
Disease of the immune system.
Septic shock (sepsis)
A dangerous condition in which the
inflammatory response goes out of control. Kills 200,000
people a year in the U.S. Results from especially severe bacterial
infections or more ordinary infections that grow rapidly worse
in patients with weakened defenses, such as the hospitalized
elderly recovering from surgery. In an inflammatory response,
neutrophils and other white blood cells secrete cytokines that
increase capillary permeability. In sepsis, continued cytokine
release makes capillaries so leaky that the bloodstream is
depleted of fluid. Blood pressure falls and the body organs shut
down, causing death in 50% of cases. Sepsis has proven difficult
to control and its incidence remains high.
Systemic lupus erythematosus (SLE)
(er
0
ĭ-the
0
mah-to
9
sus) A
systemic autoimmune disorder that occurs mainly in young
females. Diagnosis is helped by finding antinuclear (anti-DNA)
antibodies in the patient’s blood. DNA–anti-DNA complexes
(typical of type III hypersensitivity) localize in the kidneys (the
capillary filters, or glomeruli), blood vessels, brain, and synovial
membranes of joints. ±is results in glomerulonephritis, vascular
problems, loss of memory and mental sharpness, and painful
arthritis. Reddened skin lesions, particularly a “butterfly rash”
(the sign of the wolf, or
lupus
) on the face, are common.
AT T H E C L I N I C
Remember Mr. Ayers, the bus driver
from Chapter 18? When we last
saw him, he was headed for surgery.
Although his dissected aorta was
repaired, by the time surgical exposure and blood vessel clamping
had been achieved, the dissection had extended up into the origin
of his left common carotid artery. As a result, a clot formed that
caused a massive stroke. Unfortunately, this left him with severe
and permanent brain damage, and he was declared brain dead.
A discussion of Mr. Ayers’s situation with his family confirmed
his status as an organ donor. The organ recovery coordinator
evaluated Mr. Ayers’s suitability as a candidate for organ donation.
Tissue typing (histocompatibility) tests were conducted, and the
results were entered into the UNOS (United Network for Organ
Sharing) database. Two potential recipients were identified.
Mr. Ayers’s right kidney was given in transplantation to a
35-year-old man, and his left kidney was given to a 27-year-
old woman. Following surgery, both recipients were placed on
immunosuppressive drug therapy.
1.
In organ transplants, the transplanted organ is referred to as a
graft. What type of graft is represented by the two kidneys that
Mr. Ayers has donated?
2.
Tissue typing characterizes the class I and II MHC proteins.
What is an MHC protein?
3.
What is the difference between class I and class II MHC
proteins?
4.
Why is the matching of the MHC molecules and the tissue
compatibility so important in this case?
5.
Why were the recipients of the two kidneys put on
immunosuppressive drug therapy?
(Answers in Appendix H)
Immune System
Case Study
21
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