Causes

For reasons that are still not completely understood, both the T cells and the B cells become overactive in patients with RA. In an immune response it is normal for the antibody response to change over time, particularly if the first antibodies that are made do not eliminate the invading particles. Little by little, the types of antibodies being made undergo changes in an attempt to achieve better recognition and a stronger inflammatory response against a recalcitrant invader. In RA, a complex interaction between activated immune cells and an impaired antigen-elimination process leads to a greater than normal repertoire of what the antibodies recognize. Eventually, antibodies are made that recognize more of the body's own tissues in a stronger or more persistent manner than is healthy, and inflammatory responses are mounted in these tissues.

Cytokines. Most immune cells secrete or stimulate the production of powerful immune factors called cytokines. In small amounts, cytokines are indispensable for maintaining the balance of the body during immune responses, infections, injuries, tissue repair, blood clotting, clearing of debris from inflamed blood vessels, and other aspects of healing. If overproduced, however, they can cause serious damage, including dangerous levels of inflammation and cellular injury.

Cytokines are very important in the destructive process of rheumatoid arthritis, particularly those known as interleukins (ILs) -- notably IL1 and IL6 -- and tumor necrosis factor (TNF). TNF is now known to be the major cause of joint damage and various systemic manifestations of RA, including weight loss.

Leukocytes. The leukocytes, the other major white blood cells in the body, are also spurred into action by the over-zealous T cells. Leukocytes stimulate the production of key players in the inflammatory process:

• Leukotrienes attract white blood cells to the area.
• Prostaglandins open blood vessels and increase blood flow.
• Nitric Oxide is a gas that is important in blood vessel flexibility and dilation. In excessive amounts, however, it becomes a damaging substance that may play a major destructive role in RA.