Three Main Immune Defense Mechanisms
The body has three main immune defense mechanisms called “barrier functions”—that, when healthy, prevent foreign and potentially harmful substances from entering the bloodstream.
The mucous membrane barrier, consisting of the respiratory system including the throat, nasal passages, and lungs, protects us from inhaled substances (pollen, animal dander). The skin barrier keeps us safe from contacting (poison ivy, jewelry) or injected (insect bites) antigens.
The adrenal and thyroid glands are primary adjuncts to the barrier defense system, since they provide the hormones and energy essential for the proper operation of the entire immune system. When any or all of the barrier functions are broken down due to poor diet, enzyme deficiency, bacteria overgrowth, and other factors, foreign molecules are able to pass through the barriers and enter the bloodstream.
Upon its first exposure to a specific foreign molecule in the bloodstream (a process called sensitization), the immune system determines whether the substance may be harmful to the body.
If it does find the molecule to be potentially dangerous (antigen), it records the antigen’s identification information (cellular memory) and begins production of a type of protein called an antibody, which is specifically designed to deactivate the antigen.
When the body is exposed again to the antigen, the immune system identifies the antigen and mobilizes the release of the preselected antibody, setting in motion a complex series of events involving many biochemicals.
These chemicals then produce the inflammation and other typical symptoms of an allergy response.
The antibody most commonly involved in the allergic response to pollens and other aeroallergens is IgE, one of five immunoglobulin’s, or specially designed antibody proteins, involved in the immune system’s defense response to foreign substances.
Main Types Of Immunoglobulins
The main types of immunoglobulins, grouped according to their concentration in the blood, are: IgG (80%), IgA (10%45%), IgM (5%40%), IgD (less than 0.1%), and IgE (less than 0.01%).
Mast cells, which produce the allergic response and are found throughout the body’s tissues, next come into play; they tend to be concentrated in the skin, nose, and lung linings, gastrointestinal tract, and reproductive organs.
When the IgE antibody senses an allergen, it triggers the mast cells to release histamine and 28 other chemicals and the allergic response flares into action. The IgE molecules also attach themselves, like a key fitting a lock, to the allergens. Both IgG and IgM antibodies neutralize bacteria, viruses, and toxins so they can be destroyed by other white blood cells.
IgA antibodies, which are especially important in the gut, protect mucous membranes and neutralize antigens before they enter the bloodstream to trigger an allergic response. The immune function of IgD is not presently known.