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The immune system is the bodys defense mechanism. It is capable of recognizing foreign invaders such as bacteria and viruses, and destroying them. It does this through the process of inflammation. In inflammation, white blood cells are attracted to the area of invasion. The cells then are stimulated to release chemical messengers, called cytokines which help destroy the foreign invaders. The cytokine with the greatest importance in this process is tumor necrosis factor or TNF. The problem in diseases like rheumatoid arthritis is that the immune system can no longer distinguish between foreign invaders and the bodys normal cells. The immune system then begins to attack the body. TNF plays a significant role in this aberrant behavior. For a disease like rheumatoid arthritis (RA), inflammation affects the joints as well as other organ systems.

Drugs that block the effects of TNF have been found to be very effective in reducing inflammation and in slowing down the rate of disease progression in rheumatoid arthritis.

The first anti-TNF drug to be approved by the FDA in the United States was etanercept (Enbrel). This drug is actually a receptor protein that binds to circulating TNF and prevents TNF from stimulating white blood cells to produce more inflammation. It is given subcutaneously by the patient. Side effects include injection site reactions, an increased tendency for infections, rare blood cell effects, rare liver function test abnormalities, and rare neurological side-effects.

Another anti-TNF drug is infliximab (Remicade). It is an antibody that is part human and part mouse protein. This antibody is directed against TNF and removes it from the system. Remicade is given intravenously. Side effects include infusion reactions (side-effects during the intravenous infusion), increased susceptibility to infection, and reactivation of tuberculosis. Some people begin to lose their response to Remicade over time.

The third anti-TNF drug is adalimumab (Humira). This is a human antibody directed against TNF. It, like Enbrel, is administered subcutaneously by the patient. Side-effects are similar to that for Enbrel.

Patients should be counseled about the potential side-effects of these drugs prior to administration. PPD skin tests to screen for tuberculosis are advised. A chest x-ray is also something to consider. Recent data suggests that PPD skin tests should be done annually in patients receiving anti-TNF therapy.

These drugs work best when combined with methotrexate. There is increasing evidence that these drugs not only slow down the progression of RA but also reduce the incidence of cardiovascular events such as heart attacks and strokes that may occur in these patients.

Monitoring for side effects is important and a patient should be followed by an experienced rheumatologist.

It should be mentioned that these drugs dont work for everyone. Nonetheless, they are a major advancement in our arsenal of weapons against rheumatoid arthritis.

Dr. Wei (pronounced way) is a board-certified rheumatologist and Clinical Director of the nationally respected Arthritis and Osteoporosis Center of Maryland. He is a Clinical Assistant Professor of Medicine at the University of Maryland School of Medicine and has served as a consultant to the Arthritis Branch of the National Institutes of Health. He is a Fellow of the American College of Rheumatology and the American College of Physicians. For more information on arthritis and related conditions, go to: Types of Arthritis