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penicillin).
those lymphocytes that will attack them. Some factors
When a susceptible person s tissues are repeatedly ex- that might result in autoimmunity include:
17
posed to an allergen for example, exposure of the nasal
×% A change in self proteins, as a result of disease, for ex-
mucosa to pollens those tissues become sensitized; that
ample.
is, antibodies are produced in them. When the next ex-
×% Loss of immune system control, as through loss of reg-
posure to the allergen occurs, there is an antigen anti-
ulatory T cell activity, for example.
body reaction. Normally, this type of reaction takes place
×% Cross-reaction of antibodies with self antigens. This
in the blood without harm, as in immunity. In allergy,
reaction occurs in rheumatic fever, for example, when
however, the antigen antibody reaction takes place
antibodies to streptococci damage the valves of the
within the cells of the sensitized tissues, with results that
heart.
are disagreeable and sometimes dangerous. In the case of
the nasal mucosa that has become sensitized to pollen, Autoimmunity is involved in a long list of diseases, in-
cluding rheumatoid arthritis, multiple sclerosis, lupus
the allergic manifestation is hay fever, with symptoms
erythematosus, psoriasis, inflammatory bowel diseases,
much like those of the common cold.
Graves disease, glomerulonephritis, and Type I diabetes.
The antigen antibody reaction in sensitive individu-
All of these diseases probably result to varying degrees
als promotes the release of excessive histamine. Hista-
from the interaction of individual genetic makeup with
mine causes dilation and leaking from capillaries as well
environmental factors, including infections. Autoimmune
as contraction of involuntary muscles (e.g., in the
diseases are three times more prevalent in women than in
bronchi). Antihistamines are drugs that counteract hista-
men, perhaps related to hormonal differences.
mine and may be effective in treating the symptoms of
Autoimmunity is treated with drugs that suppress the
certain allergies. Sometimes, it is possible to desensitize
immune system and with antibodies to lymphocytes. Pure
an allergic person by repeated intermittent injections of
antibodies, such as these, are prepared in the laboratory
the offending allergen. Unfortunately, this form of pro-
and are known as monoclonal antibodies. A newer ap-
tection does not last long.
proach uses chemotherapy to destroy immune cells fol-
Serum sickness is an example of an allergic manifes-
lowed by their replacement with healthy stem cells from
tation that may occur in response to various sera. People
bone marrow.
who are allergic to the proteins in serum from a horse or
some other animal show such symptoms as fever, vomit-
Immune Deficiency Diseases
ing, joint pain, enlargement of the regional lymph nodes,
and urticaria (ur-tih-KA-re-ah), also called hives. This An immune deficiency is some type of failure of the im-
type of allergic reaction can be severe but is rarely fatal. mune system. This failure may involve any part of the
356 &' CHAPTER SEVENTEEN
system, such as T cells, B cells, or the thymus gland, and tibodies. These cells produce an excess of a particular an-
it may vary in severity. Such disorders may be congenital tibody, but the antibody is not effective. The disease
(present at birth) or may be acquired as a result of mal- causes loss of resistance to infection, anemia, bone pain,
nutrition, infection, or treatment with x-rays or certain and weakening of the bones, owing to production of a
drugs. factor that accelerates loss of bone tissue. High blood lev-
The disease AIDS (acquired immunodeficiency syn- els of calcium and proteins secreted by the plasma cells
drome) is a devastating example of an infection that at- often lead to kidney failure. Multiple myeloma is treated
tacks the immune system. It is caused by HIV (human im- with chemotherapy. A new approach is high-dose
munodeficiency virus), which destroys the specific helper chemotherapy combined with bone marrow transplants.
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