Rheumatoid arthritis develops when the body’s own immune system attacks the joints. This is known as autoimmunity.

The immune system is designed to detect foreign material (for example, bacteria, viruses or toxins) in the body and react by eliminating it. In autoimmune diseases, the body mistakenly identifies a component of the body as foreign and mounts an immune response against it. This results in inflammation.

Inflammation is the body’s way of healing when it is injured, infected or, in the case of autoimmune disease, when an immune response has been inappropriately stimulated. When an immune response is triggered, immune cells are activated and begin to secrete inflammatory chemicals. These chemicals cause nearby blood vessels to dilate and become leaky, to increase the blood flow to the target area and allow more immune cells and immune proteins to enter. These responses cause the characteristic signs of inflammation:

• heat and redness (from the increased flow of blood)
• pain (due to the irritation of nerve endings by inflammatory chemicals)
• swelling (from the accumulation of blood, fluid and immune cells and proteins at the site of injury)

In effect, the purpose of the inflammatory response is to concentrate the components of the immune system around a site of injury or infection so the tissues have all the cells, proteins and chemicals they need to destroy any foreign material and heal effectively. Under normal circumstances, once the trigger of the process has been eliminated, the inflammatory response abates.