Normally, the immune system functions as the body's
defense against invading germs such as bacteria and
viruses. In most allergic reactions, however, the immune
system is responding to a false alarm. When an allergic
person first comes into contact with an allergen, the
immune system treats the allergen as an invader and
gets ready to attack.
The immune system does this by generating large
amounts of a type of antibody called immunoglobulin E,
or IgE. Each IgE antibody is specific for one particular
substance. In the case of pollen allergy, each antibody is
specific for one type of pollen. For example, the immune
system may produce one type of antibody to react
against oak pollen and another against ragweed pollen.
The IgE molecules are special because IgE is the only
type of antibody that attaches tightly to the body's
mast cells, which are tissue cells, and to basophils,
which are blood cells. When the allergen next encounters
its specific IgE, it attaches to the antibody like a key
fitting into a lock. This action signals the cell to which
the IgE is attached to release (and, in some cases, to
produce) powerful chemicals like histamine, which
cause inflammation. These chemicals act on tissues
in various parts of the body, such as the respiratory
system, and cause the symptoms of allergy.
Courtesy: National Institute of Allergy and Infectious Diseases
|| San Antonio, Texas
Introduction to Allergies
What is an allergy?
What is allergic rhinitis? (Hay Fever)
Why are some people allergic?
What is an allergic reaction?
What Is Food Allergy?
Introduction to Asthma
What are Hives?