Page 177 - 84 human physiolofy part-1

The Immune System

The Allergic response

Type 1 hypersensitivity is an allergic reaction provoked by reexposure to a specific antigen.
Exposure may be by ingestion, inhalation, injection, or direct contact. The reaction is mediated by IgE
antibodies and produced by the immediate release of histamine, tryptase, arachidonate and derivatives
by basophils and mast cells. This causes an inflammatory response leading to an immediate (within
seconds to minutes) reaction.

The reaction may be either local or systemic. Symptoms vary from mild irritation to sudden death
from anaphylactic shock. Treatment usually involves epinephrine, antihistamines, and corticosteroids.

Hay Fever

Hay fever involves an allergic reaction to pollen and results in allergic rhinitis (inflammation of the
nasal mucosa). It is most common in the haying season, which is why the ailment was named hay
fever. A virtually identical reaction occurs with allergy to mold, animal dander, dust, and similar
inhaled allergens. Particulate matter in polluted air and chemicals such as chlorine and detergents,
which can normally be tolerated, can greatly aggravate the condition. The pollens that cause hay fever
vary from person to person and from region to region; generally speaking, the tiny, hardly visible
pollens of wind-pollinated plants are the predominant culprits.

Autoimmune Disorders

For reasons we do not fully understand, sometimes the immune system attacks the body the way it
normally would attack a germ or foreign substance. The genes some people inherit can contribute to
their susceptibility to develop an autoimmune disease. Most autoimmune diseases effect woman more
than men.

• In Juvenile-onset diabetes the immune system starts attacking and eliminating the cells in
the pancreas that make insulin.

• Multiple Sclerosis is a chronic degenerative disorder of the central nervous system where
the immune system starts attacking and destroying vital myelin in the brain and spinal cord.
This causes multiple sclerosis (scars) on the myelin sheath resulting in loss of nerve function.

• Another fairly known disorder is Rheumatoid Arthritis this is when the immune system
starts attacking the tissue inside your joints.

• There is another disorder, Organ and Tissue Transplants, that is classified under
immuno-deficiencies but in reality is not a failure of the immune system. In transplants, foreign
tissue is placed inside the body. These tissues do not perfectly match the surrounding cells. The
body sees this as something that should not be there and sends messages to attack and kill it.
This can make transplanting nearly impossible. This problem can not be completely prevented
but it can be diminished by making sure the donor tissue is a close match to the recipient tissue.
In addition, the recipient is placed on immuno-suppressing drugs to try and prevent the immune
system from attacking and rejecting the new organ or tissue.

Wikibooks | 177