Human Body: The Immune System

Normally, the immune system is a powerful healing mechanism.  It consists of a complex network of cells, tissues and organs located throughout the body.

• The immune system includes bone marrow, the soft center of bones.  The bone marrow is the “birth place” of blood cells.
• Lymph nodes are also part of the immune system and can be found clustered in the neck, the armpits, the abdomen and the groin.
• Parallel to the veins that carry blood is a system of lymphatic vessels.  A pale fluid, called lymph fluid, runs through these vessels.
• The spleen is part of the immune system.  It is a “meeting place” of all the body’s “fighter cells.”
• Clumps of lymph tissue are spread throughout the body to help filter out germs.  These include the tonsils and the appendix.

When a part of the body is infected, nearby lymph nodes swell up as they collect and destroy the enemy germs.  (For example, a sore throat can lead to swollen lymph nodes in the neck.)

When it is working properly, the immune system defends the body from infection and disease by identifying, attacking and eliminating any germs (like bacteria or viruses) or abnormal cells (like cancer cells).  Remarkably, the immune system can recognize and remember millions of different enemies.  Fortunately, it is usually smart enough to tell the difference between an enemy and a cell that belongs in the body.

However, there are times when the immune system fails to recognize healthy tissue as part of the body.  That is called an autoimmune reaction.