Immune system--what is it and what does it do?

Our immune system works quietly every day.  Our immune system recognizes ‘self’ and ‘non-self’ (foreign substances).  The immune system mobilizes a defense and fights infectious agents (germs, viruses, parasites, fungi) It also works to destroy cancer cells and foreign substances.  The National Institute of Allergy and Infectious Disease staff says this: “The immune system is amazingly complex.  It can recognize and remember millions of different enemies and it can produce secretions (release of fluids) and cells to match up with and wipe out nearly all of them.  The secret to its success is an elaborate and dynamic communications network.  Millions and millions of cells…gather like clouds of bees swarming around a hive and pass information bath and forth in response to an infection.  Once immune cells receive the alarm, they become activated and begin to produce powerful chemicals.  These substances allow the cells to regulate their own growth and behavior, enlist other immune cells, and direct the new recruits to trouble spots.” More information can be found at http://www.niaid.nih.gov/topics/immuneSystem/Pages/whatIsImmuneSystem.aspx