The immune system is the body's defense system against infection and disease.  The system sends specialized cells to locate, mark, and destroy harmful substances called antigens (such as bacteria, viruses, poisons) that can cause disease and infection.

Inflammation, which is also known as an inflammatory response, is one of the ways the immune system responds to the presence of antigens. Essentially, it means that the immune system (specifically white blood cells) has produced certain disease-fighting chemicals and sent them to the areas of the body affected by the antigens. The chemicals fight the antigens, but also cause the redness, swelling, and pain that we recognize as symptoms of inflammation.

Inflammation is normally acute; that is, it begins as the body starts to fight the antigens and ends when the fight is won and the immune system stops producing the chemicals. Chronic inflammation means the body continues to produce the chemicals that cause inflammation.  The immune system is, in effect, mistakenly attacking the body's own healthy tissues and organs.  This leads to autoimmune diseases, illnesses caused by the body's own defense system. 

There are many types of autoimmune diseases. They may not be able to be cured, but they can be treated and their symptoms reduced and controlled. 

Learn more about Inflammation:

Key Point 1: The immune system is the body's defense system against infection and disease. Autoimmune disease develops when this system attacks healthy cells in joints, nerves and connective tissue.