The body is protected against attack from bacteria, fungi, and viruses by the speciali ed cells and proteins in the blood and tissues that make up the immune system . White blood cells known as lymphocytes either kill invading organisms directly or produce special proteins (antibodies) to destroy them. These mechanisms are also responsible for eliminating abnormal or unhealthy cells that could othenlvise multiply and develop into a cancer.

In certain conditions it is medically necessary to clamp down the activity of the immune system. These include a number of autoimmune disorders in which the immune system attacks normal body tissue. Autoimmune disorders may affect a single organ for example, the kidneys in Goodpasture’s syndrome or the thyroid gland in Hashimoto’s disease or they may result in widespread damage, for example, in rheumatoid arthritis or systemic lupus erythematosus.

Immune system activity may also need to be reduced following an organ transplant, when the body’s defences would otherwise attack and reject the transplanted tissue. Several types of drugs are used as immunosuppressants: anticancer drugs , corticosteroids (p.99), ciclosporin , and monoclonal antibodies.

Why they are used

lmmunosuppressant drugs are given to treat autoimmune disorders, such as rheumatoid arthritis, when symptoms are severe and other treatments have not provided adequate relief. Corticosteroids are usually prescribed initially. The pronounced anti-inflammatory effect of these drugs, as well as their immunosuppressant action, helps to promote healing of tissue damaged by abnormal immune system activity. Anticancer drugs such as methotrexate may be used in addition to corticosteroids if these do not produce sufficient improvement or if their effect wanes .

lmmunosuppressant drugs are given . before and after organ and other tissue transplants. Treatment may have to be continued indefinitely to prevent rejection. A number of drugs and drug combinations are used, depending on which organ is being transplanted and the underlying condition of the patient. However, ciclosporin, along with the related drug tacrolimus, is now the most widely used drug for preventing organ rejection. It is also increasingly used to treat autoimmune disorders. It is often used in combination with a corticosteroid or the more specific drug mycophenolate mofetil. Monoclonal antibodies, which destroy specific cells of the immune system, are also used to aidtransplantation and are increasingly being used to treat autoimmune disorders. For example, adalimumab is used to treat certain types of arthritis while rituximab is also used for systemic lupus erythematosus and vasculitis.

How they work

lmmunosuppressant drugs reduce the effectiveness of the immune system, either by depressing the production of lymphocytes or by altering their activity.

How they affect you

When immunosuppressants are given to treat an autoimmune disorder, they reduce the severity of the symptoms and may temporarily halt the progress of the disease. However, they cannot restore major tissue damage.

lmmunosuppressant drugs can produce a variety of unwanted side effects. The side effects caused by corticosteroids are described in more detail on. Anticancer drugs, when prescribed as immunosuppressants, are given in low doses that produce only mild side effects. They may cause nausea and vomiting, for which an anti-emetic drug may be prescribed. Hair loss is rare and regrowth usually occurs when the drug treatment is discontinued. Ciclosporin may cause increased growth of facial hair, swelling of the gums, and tingling in the hands.

Risks and special precautions

All of these drugs may produce potentially serious adverse effects. By reducing the activity of the patient’s immune system, immunosuppressant drugs can affect the body’s ability to fight invading microorganisms, thereby increasing the risk of serious infections. Because lymphocyte activity is also important for preventing the multiplication of abnormal cells, there is an increased risk of certain types of cancer. A major drawback of anticancer drugs is that, in addition to their effect on the production of lymphocytes, they interfere with the growth and division of other blood cells in the bone marrow. Reduced production of red blood cells can cause anaemia; when the production of blood platelets is suppressed, blood clotting may be less efficient.

Although ciclosporin is more specific in its action than either corticosteroids or anticancer drugs, it can cause kidney damage and, in too high a dose, may affect the brain, causing hallucinations or seizures. Ciclosporin also tends to raise blood pressure, and another drug may be required to counteract this effect .

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