Allergies – Understanding the Immune System

Allergies – Understanding the Immune System

I just had a customer tell she thought she feels like she is waging war when it comes to dealing with her allergies. In many ways getting control over your allergies is like war. Over the next few post we will be talking about how we can live with our allergies and maybe just win the war.

Understanding the Immune System

We know allergy is a chronic condition of the immune system.  This means it can be controlled but it cannot be cured.  In order to understand allergies, you must first understand the immune system. 

The job of the immune system is to protect the body from outside invaders, whether they are bacteria, viruses, fungi or parasites.  The immune system has a marvelous memory.  It can remember millions of enemies and for each enemy it has a remembered plan of destruction.  Unfortunately, not all enemies identified by the immune system are true enemies.

Self & Nonself

The heart of the immune system is the ability to distinguish between self and nonself. 

Virtually every cell in our body carries molecules that identify it as self. The body's immune defenses do not normally attack tissues that carry a self identifier. When the “defenders” of our immune system encounter cells or organisms carrying molecules that say "foreign invader" the immune troops move quickly to eliminate the intruders.

Any substance capable of triggering an immune response is called an antigen, which means “nonself”.

Antigens can be a virus, a bacterium, a fungus, or a parasite or even the tissue from a transplant.  An antigen announces its “foreignness” by means of characteristic shapes called epitopes, which protrude from its surface. 

In abnormal situations, the immune system gets self and nonself confused and launches an unwarranted attack on the body’s own cells.  This referred to as an autoimmune disease and includes certain types of diabetes and arthritis.

The Immune Arsenal

The immune system army is spread throughout the body.  Bone marrow is the home of all blood cells.  All immune cells start as stem cells in the marrow.  As a response to cytokines, they grow up into special types of cells called lymphocytes, which are specialized white blood cells. Lymphocytes can be B cells, phagocytes or T cells. 

The thymus is the T cell staging area. T cells (thymus lymphocytes) mature in the thymus before heading out to other tissues.  Lymph nodes are spread throughout the body from the head (the tonsil area) to the legs (the popliteal node in the knee area).  

Lymphocytes collect in the lymph nodes and move throughout the body using the blood vessels.  While moving through the body, they are on patrol, watching for nonself cells and other enemy invaders.

Keeping Out Foreign Invaders

The immune system stockpiles a tremendous arsenal of cells.  In order to have room to match millions of possible foreign invaders, just a few of each type of antibody is stored.

When an antigen appears, those matched cells quickly multiply into a full-scale army.  Antibodies are made as a result of antigen identification by the B cells.  Each B cell recognizes one specific antigen. 

There is one antigen for a cold to which you have been exposed and a different antigen for the measles.  These antibodies come from plasma cells that are created when the B cells identify an antigen. 

The antibodies can attack an antigen but they cannot penetrate it. Antibodies belong to a family of large molecules known as immunoglobulin.

Immunoglobulins are proteins, made up of chains of amino acids.  Scientists have identified nine chemically distinct classes of human immunoglobulin (Ig).  Each type plays a different role in the immune defense strategy.

For example, IgM works against bacteria.  But it is the IgE, which normally occurs only in trace amounts, that is the villain in allergic reactions. Each IgE antibody is specific; one reacts against oak pollen, another against ragweed

False Alarm

The first time an allergy-prone person is exposed to an allergen, he or she makes large amounts of the corresponding IgE antibody. These IgE molecules attach to the surfaces of mast cells in the body.   

So, if you are allergic to the protein found in the body and feces of the farinae dust mite (Der f1) the first time you are exposed to the protein your body creates an IgE antibody for that antigen. 

The next time you are exposed to that protein, the IgE antibody will signal the body to begin powerful chemical warfare. These chemicals include histamine, heparin, eosinophils and neutrophil.

Next up - Your Nose Knows the Symptoms, Do You?

Till next time