What is being tested?
Interleukin-6 (IL-6) is a protein produced by various cells. It helps regulate immune responses, which makes the IL-6 test potentially useful as a marker of immune system activation. IL-6 can be elevated with inflammation, infection, autoimmune disorders, cardiovascular diseases, and some cancers. The test measures the amount of IL-6 in the blood.
Interleukin-6 is one of a large group of molecules called cytokines. Cytokines have multiple roles to play within the body and act especially within the immune system to help direct the body’s immune response. They are a part of the “inflammatory cascade” that involves the coordinated, sequential activation of immune response pathways.
IL-6 acts on a variety of cells and tissues. It promotes differentiation of B-cells (white blood cells that produce antibodies), promotes cell growth in some cells, and inhibits growth in others. It stimulates the production of acute phase proteins. IL-6 also plays a role in body temperature regulation, bone maintenance, and brain function. It is primarily pro-inflammatory but can also have anti-inflammatory effects.
How is the test used?
Interleukin-6 (IL-6) may be used to help evaluate a person who has a condition associated with inflammation, such as lupus or rheumatoid arthritis, or with infection, such as sepsis. It may also be used in the evaluation of diabetes, stroke, or cardiovascular disease.
When is it ordered?
The IL-6 test is not frequently ordered. C-reactive protein (CRP) is the most commonly ordered test to evaluate inflammation, but IL-6 may be ordered in conjunction with or following a CRP test when a person has signs and symptoms of an inflammatory condition or infection and a health care practitioner wants additional information.
What does the test result mean?
Normally, IL-6 is not detected in the blood or is present in low levels.
An elevated IL-6 may mean that the person tested has an inflammatory condition. IL-6 is elevated with a variety of conditions and has been associated in some cases with an increased risk of disease development or worsening prognosis. An increase in IL-6 may be seen in conditions such as:
- Rheumatoid arthritis, lupus, and other autoimmune disorders
- Some cancers
- Cardiovascular disease
Is there anything else I should know?
Tocilizumab, a drug that targets the IL-6 receptor and blocks the action of IL-6, is being prescribed to some patients with rheumatoid arthritis. This drug reduces inflammation and slows the progression of joint destruction. Additional drugs that target IL-6 (or other cytokines) are being researched and developed.
The usefulness of the IL-6 test in the medical setting is still being established. Medical researchers are actively studying IL-6 and other cytokines to better understand the normal functions of these proteins within the immune system and their association with a variety of diseases and conditions. The goal is to determine whether IL-6 is causing or contributing to disease states. This will show how it may be used to help in the diagnosis, treatment, and monitoring of diseases. It may be used to help guide treatment or even as a target for the treatment of these conditions.
Can IL-6 be measured in samples other than blood?
Interleukin-6 may sometimes be measured in other body fluids, such as joint fluid (synovial fluid) and cerebrospinal fluid.
How long will it take for my results?
This is not a routine test and not all laboratories offer this test. It is most likely that your sample will be sent to a reference laboratory for testing and it may take from one to several days for results to be available.
Can I lower my IL-6 level?
Concentrations of IL-6 will decrease with a decrease in inflammation but there is not currently evidence that IL-6 levels respond to lifestyle changes.