Immunosuppressive therapy is one of the standard first treatments for many patients with severe aplastic anemia. The other standard treatment is a bone marrow or cord blood transplant (BMT). This page provides some details about immunosuppressive therapy for severe aplastic anemia. For an overview of severe aplastic anemia and how it may be treated, see Aplastic Anemia (Severe).
The immune system is made up of organs and specialized cells that work together to protect the body from infection and disease. The immune system uses white blood cells to fight infections. The white blood cells mark and attack cells that they do not recognize as belonging in the body. Immunosuppressive therapy uses drugs that suppress (weaken) the immune system. This treatment is based on the widely accepted theory that aplastic anemia is a result of the immune system attacking the bone marrow. The treatment weakens the immune system's response and allows the marrow to make more blood cells.
The most effective combination of drugs known today is:
- Antithymocyte globulin (ATG) — a drug that targets a type of white blood cell called T cells. T cells are an important part of the immune system. T cells direct the rest of the immune system when to attack foreign cells such those that cause infection. They also help in the attack.
- Cyclosporine — a drug that targets T cells.
- Methylprednisolone — a drug that causes the immune system to make fewer antibodies and that is used to reduce the side effects of ATG.
Other immunosuppressive drugs may be used if the standard combination does not work. Some of these drugs are being studied in clinical trials.
Immunosuppressive drugs can cause side effects, including fever, high blood pressure and problems with kidney function. Most of these side effects are temporary. However, a long-term side effect is a higher risk of getting a secondary disease such as myelodysplastic syndrome (MDS), leukemia or another type of cancer. In one long-term study, 11 years after starting immunosuppressive therapy, the risk of developing a secondary disease was 25%. 
It is a good idea to ask your doctor for help interpreting these data and any other outcomes data you find. Your doctor can provide context for these data and discuss your specific situation with you. For more things to consider, see Understanding Survival Outcomes Data
In about 60% to 77% of people, the standard drug combination brings a response (increases blood counts). [1, 2, 3] In clinical studies, the overall likelihood of survival at five or more years after treatment with immunosuppressive therapy has been reported at 55% to 87%, varying with age and other factors. [2, 3] For many people, blood counts do not reach normal levels, but are high enough that they can stop receiving blood transfusions.
For some groups of patients, these long-term survival rates are similar to those achieved with transplants — see Severe Aplastic Anemia Transplant Outcomes. However, after immunosuppressive therapy, patients' responses are often not as complete and are less likely to last than after a successful transplant. After immunosuppressive therapy, many people need to repeat treatment or take cyclosporine for the long term. In one study, 26% of patients needed to continue treatment with cyclosporine for five to 12 years.  In another study, five years after starting treatment, only 38% of patients were able to stop taking cyclosporine. 
It often takes about three months after starting immunosuppressive therapy before a person's blood counts are high enough for him or her to stop receiving blood transfusions. Patients who do not show a response within three to four months should talk with their doctor about their treatment options. Many patients respond to a second immunosuppressive therapy treatment — in one study, 23 of 30 patients who received a second treatment (77%) were able to stop receiving transfusions.  However, for some patients, a transplant may offer a better chance of long-term survival without return of the disease.
For more information about making treatment choices, see Aplastic Anemia (Severe).
- Frickhofen N, Heimpel H, Kaltwasser JP, Schrezenmeier H, for the German Aplastic Anemia Study Group. Antithymocyte globulin with or without cyclosporin A: 11-year follow-up of a randomized trial comparing treatments of aplastic anemia. Blood. 2003; 101(4):1236-1242.
- Rosenfeld S, Follmann D, Nunez O, Young NS. Antithymocyte globulin and cyclosporine for severe aplastic anemia: association between hematologic response and long-term outcome. JAMA. 2003; 289(9):1130-1135.
- Bacigalupo A, Bruno B, Saracco P, et al. Antilymphocyte globulin, cyclosporine, prednisolone, and granulocyte colony-stimulating factor for severe aplastic anemia: an update of the GITMO/EBMT study on 100 patients. Blood. 2000; 95(6):1931-1934.
- Di Bona E, Rodeghiero F, Bruno B, et al. Rabbit antithymocyte globulin (r-ATG) plus cyclosporine and granulocyte colony stimulating factor is an effective treatment for aplastic anaemia patients unresponsive to a first course of intensive immunosuppressive therapy. Br J Haematol. 1999; 107(2):330-334.
C. F. LeMaistre, M.D., Southwest Texas Methodist Hospital, San Antonio, Texas
Paul Shaughnessy, M.D., Texas Transplant Institute, San Antonio, Texas
Anthony S. Stein, M.D., City of Hope National Medical Center, Duarte, Calif.