In the treatment of rheumatological diseases, doctors often use a class of drugs called “immunosuppressants”. As the name suggests, immunosuppressants can lower the immunity of the body, but when do we need to lower the immunity? Isn’t it better to have a high immunity? Can immunosuppressants cause a lot of harm to the body? What are the most commonly used immunosuppressive drugs? What are the side effects of all of them? Let me answer all the above questions for you one by one now. Under normal circumstances, the immune function of the body is maintained in a balanced state. Immunity is not the higher the better, too strong immunity will cause damage to the body, too weak immunity is vulnerable to external harmful substances. The immune function of rheumatism patients is often activated abnormally, that is, the immunity is too strong. If the immune function is not controlled in time, the immune inflammatory reaction will occur, causing inflammation and damage to the body’s tissues and organs. The most commonly damaged organs are joints, skin, kidneys, etc. Therefore, many patients with rheumatic immune diseases show symptoms such as joint pain, rash and erythema, and abnormal urination. In order to control the overactive immune response, reduce inflammation and mitigate organ damage, we need to use immunosuppressants. When reading the drug instructions of immunosuppressants, we will find that many immunosuppressants are indicated for tumor treatment. Patients will have many doubts, is immunosuppressant equal to anti-tumor drugs? I am not a tumor, why should I use anti-tumor drugs? Will the use of these drugs cause great harm to the body? Indeed, tumor patients also need to use immunosuppressants. Because there are tumor cells in the body of tumor patients, these cells have common characteristics with the immune cells in the body of rheumatologic patients. They both grow uncontrollably and indiscriminately. Tumor patients need to use immunosuppressants to control the growth of tumor cells. However, tumor cells are more difficult to be removed than immune cells, so the dose of immunosuppressants used in anti-tumor therapy is often very high. In contrast, the dosage of immunosuppressants used in rheumatological diseases is small, so the incidence of side effects is also low and does not affect the body greatly. This shows that immunosuppressants are not equivalent to antineoplastic drugs. Immunosuppressants are antirheumatic drugs when the dosage is small, and they are antitumor drugs when the dosage is large. There are many kinds of immunosuppressants applied clinically, and each of them has different mechanisms of action, but they all share the common feature of being able to suppress immune cells and reduce inflammatory factors. Specialists will choose the appropriate immunosuppressant according to the characteristics of each drug and the actual situation of the patient. Steroidal anti-inflammatory drugs are the most commonly used immunosuppressants, which are often called “hormones”, such as prednisone, dexamethasone and methylprednisolone. “Hormones” have a wide range of effects, including anti-inflammatory, anti-rheumatic, anti-allergic and immunosuppressive effects. It can effectively inhibit inflammatory factors and reduce various immune cells. Clinically, for patients with strong immune response and severe inflammation, the use of hormones can have an “immediate” effect. However, hormones are a “double-edged sword”, as they have good clinical effects and may also have a wide range of side effects. Osteoporosis, increased blood sugar, increased blood pressure, body fat, and peptic ulcers are some of the common adverse effects of hormones. These adverse reactions are often seen in patients who have been using hormones for a long time and in large amounts. Therefore, when a specialist uses hormones, he or she will closely observe the condition and start reducing or stopping the use of hormones as soon as the condition is under control. At the same time, doctors often combine the medication with calcium supplementation and stomach protection to minimize the side effects of the drugs. Methotrexate, leflunomide, hydroxychloroquine and other immunosuppressants, they can be defined as slow-acting immunosuppressants. They are by interfering with the synthesis of DNA and RNA, thus stopping the haphazard growth of immune cells. And hydroxychloroquine can interfere with immune cell synthesis in addition, it can also limit the activity of immune cells, so that to immune response is limited. They can effectively reduce various rheumatic antibodies and play a “curative” role in the treatment of rheumatic immune diseases, so they are widely used in rheumatoid arthritis, systemic lupus erythematosus and other connective tissue diseases. However, because they can only inhibit the synthesis of immune cells, their effect on the activated immune cells is weak. Clinically, clinical symptoms usually start to improve only after 2 to 3 months of taking the drug and after the original activated immune cells are metabolized naturally, so they are called slow-acting immunosuppressants. Therefore, in clinical use, physicians usually add other anti-inflammatory and analgesic drugs or hormones to enhance symptom control early in the dosing process. Doctors also often combine two or three of the slow-acting drugs at the same time to enhance their effectiveness. There is also a group of immunosuppressive drugs that are more potent and are generally used in patients who are more severely ill, or who have developed organ damage. Representative drugs are: cyclophosphamide and azathioprine. These immunosuppressants kill immune cells directly, and immunosuppression is stronger and faster. However, the side effects of these drugs are also significant, and they are prone to co-infection, hepatic and renal toxicity, and gonadal suppression during use. Therefore, during the use of these drugs, doctors will ask patients to follow up more frequently in order to adjust the drugs in time. With the development of medicine, new types of immunosuppressive drugs have been introduced into the clinic, usually acting on a key cytokine or a key inflammatory pathway. Each immunosuppressant has different effects and adverse reactions. Rheumatologists are experts in the use of immunosuppressive drugs, and they are familiar with the properties of each immunosuppressive drug and will develop individualized immunosuppressive regimens for each patient. You should not give up treatment because you are afraid of the side effects of immunosuppressive drugs. As long as the immunosuppressive drugs are used under the guidance of a rheumatologist, we will be able to cure rheumatologic diseases safely and without toxicity.