Suppressed Immune System

What Is It, Causes, and More

Author: Corinne Tarantino, MPH

Editors: Alyssa Haag, Kelsey LaFayette, BAN, RN

Illustrator: Jillian Dunbar

Copyeditor: Joy Mapes

Modified: 4 Jan 2024

What is a suppressed immune system?

The immune system consists of the body’s defenses against most foreign bodies (i.e., pathogens), and it includes white blood cells, antibodies, organs (e.g., the lymphatic organ system, spleen, thymus) and other parts of the body. When a body lacks sufficient white blood cells or antibodies, the immune system is considered suppressed. A suppressed immune system is weakened to the point that it cannot mount a proper immune response to protect the body from pathogens, such as bacteria, viruses, and other infectious microorganisms. Therefore, people with a suppressed immune system become vulnerable to various infectious diseases.

What causes immune suppression?

There are many different causes of immune suppression, including diseases, medications, and lifestyle factors. 

Most commonly, a suppressed immune system can be caused by an autoimmune disease, in which the immune system attacks its own cells. This occurs when the immune system produces self-targeting antibodies, which cannot distinguish between self and non-self and will therefore mistakenly attack an individual’s own body. Some of the most common autoimmune diseases include systemic lupus erythematosus, rheumatoid arthritis, and type 1 diabetes. Both systemic lupus erythematosus and rheumatoid arthritis are characterized by inflammation or swelling of the joints, while type 1 diabetes is characterized by impaired release of the insulin, a naturally occurring hormone that regulates blood sugar levels, from the pancreas.

There are various viral and bacterial infections that can also suppress the immune response. The most common example of long-term viral immunosuppression is the human immunodeficiency virus (HIV), which can develop into acquired immune deficiency syndrome (AIDS). HIV infects and destroys CD4+ T cells, a major group of white blood cells involved in responding to viral pathogens. This leaves the immune system suppressed and vulnerable to other infections. Pneumonia is another example. Often the result of a bacterial infection (e.g., Staphylococcus aureus or Streptococcus pneumoniae), pneumonia causes inflammation of the lungs. The damage pneumonia can do to the lungs can suppress the immune system and increase the risk of future infections. 

Other diseases -- including lymphoma, leukemia, and sickle cell disease -- may also suppress the immune system, as they can affect the spleen, an important organ involved in the immune response. Lymphoma and leukemia are types of cancer that can cause a buildup of lymphoma cells, red blood cells, and platelets in the spleen. This buildup can make the spleen swell and work less efficiently, which may eventually lead to splenic dysfunction. In the case of sickle cell disease, the characteristic sickle-shaped red blood cells can block the spleen’s  blood vessels, causing swelling and impairing the spleen’s functioning.

Rarely, an individual may be born with poor development or functioning of one or more immune cell types, called a primary immune deficiency. These conditions typically affect the four main types of antibodies: IgA, IgE, IgG, and IgM. Each type of antibody plays various roles in fighting off pathogens. The most common types of primary immunodeficiencies include selective IgA deficiency (i.e., deficiency in the IgA antibody), X-linked agammaglobulinemia (i.e., deficiency in all classes of antibodies), and hyper-IgM syndrome (i.e., deficiency in IgA, IgE, IgG antibodies).   

Moreover, there are several medications that can weaken the immune system. Immunosuppressants are a class of medications that are prescribed intentionally to suppress the immune system, such as to treat an autoimmune disease or prevent the body from rejecting an organ transplant. Immunosuppression can also be a side effect of some treatments, like chemotherapy. Prescribed to destroy cancer cells, chemotherapy medications often suppress the immune system at the time of treatment and for a few months following the conclusion of treatment.

Occasionally, lifestyle factors, such as long-term alcohol misuse and severe malnutrition, may also result in a weakened immune system. 

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What are the signs and symptoms of a suppressed immune system?

Signs and symptoms of a suppressed immune system include frequent infections accompanied by severe constitutional symptoms, such as high fevers, chills, and weakness. Also, if an individual requires many antibiotic treatment courses in one year, this may be indicative of an underlying immune response concern. Specifically, the American Academy of Allergy, Asthma & Immunology suggests that if a child needs more than four antibiotic courses in a year, or an adult needs more than two, a healthcare professional should assess for underlying immune suppression. For both children and adults, having pneumonia twice in a lifetime, needing preventative antibiotics, or having chronic sinus infections may also indicate a suppressed immune system.

Depending on the cause of the immunosuppression, there may be additional symptoms, such as feeling tired and weak or experiencing body aches and pains. Some autoimmune diseases may present with swelling around the joints and rashes on the skin. For example, people with lupus tend to have a distinctive “butterfly” rash across both cheeks; however, unlike rashes caused by an allergic reaction, it is usually not an itchy rash.

How is a suppressed immune system diagnosed?

Diagnosis often begins with a medical examination, during which a clinician asks for the individual's past medical and family history, assesses their signs and symptoms, and performs a physical exam. If immunosuppression is suspected, blood tests will often be performed, particularly a complete blood count (CBC). A CBC will measure how many white blood cells an individual has, and it can provide additional information that may help to identify what part of the individual’s immune system is suppressed. Additional blood tests may be performed depending on the suspected cause. In some cases, imaging, such as an X-ray or magnetic resonance imaging (MRI), may assist with diagnosis.

How is a suppressed immune system treated?

Individuals with a suppressed immune system will often be monitored for the development of infectious diseases, and they can be educated on infection prevention measures, including guidelines for self-isolation and personal protective equipment (PPE). An individual may also practice lifestyle behaviors that support their immune system, such as getting adequate sleep, exercising regularly, and eating a balanced diet with lots of fruits and vegetables. If infection occurs, antibiotics, like amoxicillin, or antivirals, like oseltamivir, may be prescribed depending on the specific bacterial or viral cause. Additional treatment for a suppressed immune system will vary by the underlying cause. 

For autoimmune diseases, immunosuppressive medications are often prescribed. HIV may be treated with antiretroviral therapy (ART), which aims to keep the virus from spreading throughout the body. HIV, as well as some cancers, may also be treated with immunomodulation therapy, medications that aim to improve and strengthen the immune response

A person with splenic dysfunction may have a splenectomy, or surgery to remove their spleen. Although an individual can survive without a spleen, this will increase their risk of infection and sepsis. Because individuals without a spleen are at an increased risk of infections from encapsulated bacteria, vaccination against pneumococcus, meningococcus, and Haemophilus influenzae is advised after splenectomy. 

For primary immune deficiency diseases, intravenous immunoglobulin treatments may be given to provide the individual with the specific antibodies they lack. Treatment can also include stem cell transplants or gene therapy, which promote the body’s intrinsic production of antibodies. 

When the immunosuppression is caused by a medication, treatment usually focuses on relieving the unwanted side effects. Such treatment can include medications to treat nausea (e.g., ondansetron) and pain-relieving medications (e.g., aspirin, ibuprofen). If an infection occurs, the immunosuppressant’s dosage may be lowered, and depending on the infectious agent, antibiotics or antivirals may be prescribed. Less commonly, the immunosuppressive medication may be discontinued.  

What are the most important facts to know about a suppressed immune system?

A suppressed immune system is weakened to the point that it leaves an individual vulnerable to infections. Immune system suppression can result from many causes, including diseases, medications, and lifestyle factors. Most commonly, immune suppression happens due to an autoimmune disease, such as lupus, rheumatoid arthritis, or type 1 diabetes. The occurrence of frequent infections with severe symptoms is the primary sign of a suppressed immune system. Immunosuppression is often diagnosed through a medical examination and blood tests, typically including a complete blood count (CBC). Most immunosuppression is treated by monitoring for infections, practicing lifestyle behaviors that boost the immune system, and taking medications to treat the associated symptoms and underlying cause.

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Related links

Immunodeficiencies: Clinical practice
Immunodeficiency disorders - Primary: Nursing
Immunodeficiency disorders - Secondary: Nursing

Resources for research and reference

Bow, E. J. (2014). Approach to infection in patients receiving cytotoxic chemotherapy for malignancy. In J. Hall, G. Schmidt, & J. Kress (Eds.), Principles of critical care (4th ed.). McGraw-Hill Education. 

Diamond, B., & Lipsky, P. E. (2018). Autoimmunity and autoimmune diseases. In J. L. Jameson, A. Fauci, D. Kasper, S. Hauser, D. Longo, & J. Loscalzo (Eds.), Harrison's principles of internal medicine (20th ed.). McGraw-Hill. 

Fernandez, J. (2021). Overview of immunodeficiency disorders. In Merck Manual: Consumer Version. Retrieved May 27, 2021, from 

Fischer, A. (2018). Primary immune deficiency diseases. In J. L. Jameson, A. Fauci, D. Kasper, S. Hauser, D. Longo, & J. Loscalzo (Eds.), Harrison's principles of internal medicine (20th ed.). McGraw-Hill. 

Koch, R. Kox, M., de Jonge, M., van der Hoeven, J., Ferwerda, G., Pickkers, P. (2017). Patterns in bacterial- and viral-induced immunosuppression and secondary infections in the ICU. Shock (Augusta, Ga.), 47(1): 5-12. DOI: 10.1097/SHK.0000000000000731

Krensky, A., Azzi, J., & Hafler, D. (2017). Immunosuppressants and tolerogens. In L. Brunton, R. Hilal-Dandan, & B. Knollmann (Eds.), Goodman & Gilman's: The pharmacological basis of therapeutics (13th ed.). McGraw-Hill Education. 

Lake, D., & Briggs, A. (2021). Immunopharmacology. In B. Katzung, & T. Vanderah (Eds.), Basic & clinical pharmacology (15th ed.). McGraw-Hill. 

Levinson, W., Chin-Hong, P., Joyce, E., Nussbaum, J., & Schwartz, B. (2020). Review of medical microbiology & immunology: A guide to clinical infectious diseases (16th ed.). McGraw-Hill. 

McCusker, C., & Warrington, R. (2011). Primary immunodeficiency. Allergy, Asthma, & Clinical Immunology: Official Journal of the Canadian Society of Allergy and Clinical Immunology, 7 Suppl 1(Suppl 1): S11. DOI: 10.1186/1710-1492-7-S1-S11

Papadakis, M., McPhee, S., & Bernstein, J. (2020). Quick medical diagnosis & treatment 2020. McGraw-Hill Education.

Ryan, K. (2017). Sherris medical microbiology (7th ed.). McGraw-Hill Education.