Causes

Causes

Although much has been learned about the process leading to rheumatoid arthritis, researchers have yet to uncover all the factors that lead to this devastating disease. One prevalent theory is that a combination of factors triggers rheumatoid arthritis, including an abnormal autoimmune response, genetic susceptibility, and some environmental or biologic trigger, such as a viral infection or hormonal changes.

The Immune Response and Inflammatory Process

The Normal Immune System Response. The inflammatory process is a byproduct of the activity of the body's immune system, which fights infection and heals wounds and injuries:

• When an injury or an infection occurs, white blood cells are mobilized to rid the body of any foreign proteins, such as a virus.
• The masses of blood cells that gather at the injured or infected site produce factors to repair wounds, clot the blood, and fight any infections.
• In the process the surrounding area becomes inflamed and some healthy tissue is injured. The immune system is then called upon to repair wounds by clotting off any bleeding blood vessel and initiating fiber-like patches to the tissue.
• Under normal conditions, the immune system has other special factors that control and limit this inflammatory process.

The Infection Fighters. Two important components of the immune system that play a role in the inflammation associated with rheumatoid arthritis are B cells and T cells, both of which belong to a family of immune cells called lymphocytes.

When macrophages recognize foreign particles entering the bloodstream, they are programmed to ingest them, split them into pieces, and bring specific sections of them (antigens) into contact with the surface of the T cell. These antigens are placed within specialized proteins on the surface of the T cell that signal to a T cell and begin a process of immune system inspection. This process involves the interaction of several proteins on B cells and T cells, which seem to signal back and forth.

If the T cell recognizes an antigen as "non-self," then it will produce chemicals (cytokines) that cause B cells to multiply and release many immune proteins (antibodies). These antibodies circulate widely in the bloodstream, recognizing the foreign particles and triggering inflammation in order to rid the body of the invasion. T cells can be further categorized as killer T cells or helper T cells. Killer T cells directly attack antigens, such as viruses and tumor cells. Helper T cells recognize antigens that are presented to them by macrophages (or other specialized cells), and can stimulate B cells to mount various kinds of attacks on the antigen. They also produce chemicals (cytokines) that can have a more direct role in the inflammatory process.