Immunosuppression involves inhibiting or suppressing undesirable defense responses of the body’s immune system. This procedure is indicated primarily for patients with transplants and autoimmune diseases because the defense system of such patients might otherwise damage the body’s own tissues. Immunosuppression is associated with risks such as increased susceptibility to infection and side effects such as nausea.
What is immunosuppression?
Immunology is concerned with the biological and biochemical basis of the body’s defense system. For example, pathogens such as bacteria and viruses and otherwise foreign substances and environmental toxins initiate immune responses. In the case of various disorders and malfunctions of the defense mechanisms, the recognition and inactivation of exogenous substances by the immune system no longer proceeds smoothly. The human immune system plays a central role in numerous diseases. All disorders of the immune system are therefore also the subject of immunology. The same applies to therapeutic approaches with an immunological basis. One such approach is immunosuppression. This involves the therapeutic suppression of all immune processes. Immunosuppressants are used to inactivate immunologically undesirable as well as misdirected processes and have proven to be an established therapeutic component in various indications. Interferon is one of the best-known immunosuppressants. The modes of action of immunosuppressive drugs are divided into extracellular and intracellular effects.
Function, effects, and targets
In immunosuppression, external intervention unphysiologically inhibits or suppresses the immune response. Therapeutic immunosuppression can occur at several levels. Common to all levels is intervention in the synthesis or signaling pathways of the immune system. One possibility for such intervention is the inhibition or destruction of immune stem cells in the bone marrow. Apart from this, protein biosynthesis in immunocompetent cells can be inhibited by immunosuppression. Immunocompetent cells produce antibodies. Their inhibition thus results in decreased antibody production, which has the effect of immunological weakening. In addition, immunosuppression can interrupt or block interleukin-mediated signaling pathways in immunological lymphocytes. Thus, the regulation of the immune system is influenced from the outside and can be adapted to the individual case. Different conditions provide an indication for immunosuppressive treatment. As a rule, immunosuppressants are used whenever immunological processes would cause harm to an organism. This is the case, for example, in transplantation. If the immune system recognizes the transplanted organ or tissue as foreign to the body, it drives an attack on the foreign substance and thus initiates a rejection reaction. Since the standard introduction of immunosuppression prior to transplantation, the risks for rejection reactions have decreased substantially. Immunosuppression plays an equally relevant role for patients with autoimmune diseases. Autoimmune diseases are diseases with excessive immune system reactions directed against the body’s own tissues instead of pathogens. The patient’s immune system thus recognizes the tissue of the patient’s own body as a foreign body to be fought and causes severe inflammatory reactions in the affected structures. This can result in organ damage, in the case of multiple sclerosis, for example, irreversible damage and consequent loss of brain function. Patients with allergies are also often given immunosuppressants on a permanent basis. Allergies are hypersensitivities of the immune system that can be suppressed or at least attenuated by immunosuppressive therapies. As a rule, immunosuppression in allergy and autoimmune patients takes the form of prophylactic long-term drug treatment. While transplantation, allergy, and autoimmune disease are medical indications for therapeutic immunosuppression, the body may also be involuntarily affected by immunosuppression. Pathological immunosuppression is known to exist in diseases such as HIV. Immunodeficiency is the result. Weakening of the immune system can also be observed in the immunosuppressive effects of UV-B radiation.Excessive UVB exposure of the skin therefore promotes the development of malignant skin tumors and reduces the defense against pathogens such as fungi and bacteria. In addition, physical and psychological overload lead to suppression of various immune parameters. This immunosuppressive effect is known to lead to susceptibility to infections in overload situations.
Risks, side effects, and hazards
Therapeutic immunosuppression is associated with significant risks and side effects. This is especially true for oral immunosuppressants, which do not act locally but exert their effects throughout the body. Targeted suppression of individual parameters has been impossible to date. Therefore, immunosuppression dampens the immune system as a whole. The body is less protected from both infection and cancer cells as a consequence. A common side effect of immunosuppression is mucositis, an inflammation of the mucous membranes. Often this reaction occurs with chemotherapy or radiation therapy, in which case it is referred to as radiogenic mucositis. The inflammatory reaction can spread throughout the digestive tract. In immunocompromised patients and patients with autoimmune diseases, mucositis usually corresponds to an infection with various pathogens. The weakened immune system of these patients is particularly susceptible to pathogens such as fungi, viruses or bacteria. These pathogens cause inflammation of the mucous membranes, which physicians are also familiar with from patients in poor general and nutritional condition, elderly patients or HIV patients. Some immunosuppressants are also associated with side effects such as blood pressure disorders, blood sugar abnormalities and cholesterol elevation. In addition to the kidneys and nerves, many of the drugs stress the liver, cause nausea and even vomiting, or damage the gastrointestinal tract. Depending on the active ingredient, fatigue, depression and confusion may also occur. Specifically, the risks and side effects of immunosuppressive therapy depend greatly on the particular drug and the dose administered. Because of the numerous risks and side effects, the advantages and disadvantages of immunosuppressive therapy must be weighed individually for each patient. Only when the benefits clearly outweigh the risks is treatment indicated.
