IgM is a type of antibody that binds to and neutralizes potentially harmful substances. Your immune system makes it as part of the initial response to things like germs.
Your immune system is crucial for protecting you from germs, cancers, and other potentially harmful substances. It’s made up of a network of different tissues and cell types.
Antibodies, also called immunoglobulins, are Y-shaped proteins that specifically target and neutralize foreign substances like germs. Immunoglobulin M (IgM) is one type of immunoglobulin.
Continue reading to learn more about IgM, what high and low IgM levels may mean, and more.
IgM is one of the five different antibody types. In fact, it’s actually the first type of antibody on the scene when your immune system detects and responds to a foreign substance, called an antigen.
Generally speaking, antibodies are made by a type of immune cell called a B cell. When B cells detect an antigen, they can change into specialized cells called plasma cells.
During the early stages of the immune response, plasma cells make and release IgM into the bloodstream. IgM can then go on to bind to and neutralize the antigen.
Plasma cells release IgM as a pentamer, which basically means it’s made up of five individual antibodies linked together. To visualize this, imagine a circle of five letter Ys connected at their base.
The unique structure of IgM has a purpose. A single IgM antibody has only two sites with which to bind to an antigen. What’s more, these sites bind to antigens rather weakly.
However, the pentamer structure provides 10 binding sites. This strength in numbers allows IgM to more effectively bind to and neutralize antigens.
Levels of IgM in the blood can be measured by testing. The average concentration of IgM in the bloodstream is
If your IgM levels are being tested, a normal range is between 0.45 and 2.5 mg/ml. Having IgM levels above or below this range could be a sign of an underlying medical condition.
Certain factors can impact your IgM levels, causing them to become higher or lower than normal. Let’s explore some potential causes of high and low IgM levels below.
Causes of high IgM levels
As far as antibodies go, IgM is a first responder. That means that higher IgM levels can indicate the presence of a new infection.
However, high IgM can also mean that your immune system is dealing with a chronic health issue. Some examples include:
- rheumatoid arthritis, an autoimmune disease that damages the joints
- primary biliary cholangitis, a disease that causes damage to the liver’s bile ducts
- nephrotic syndrome, which happens due to kidney damage
- X-linked hyper IgM syndrome, a genetic condition where the body has too much IgM and too little of other antibody types
- Schnitzler syndrome, an inflammatory condition associated with skin rash high IgM
- IgM monoclonal gammopathy of undetermined significance (MGUS), a precancerous condition where plasma cells make high levels of abnormal IgM
- Waldenström macroglobulinemia, a type of non-Hodgkin’s lymphoma that affects B cells and leads to production of high levels of abnormal IgM
- IgM myeloma, a rare type of multiple myeloma associated with high levels of abnormal IgM
Causes of low IgM levels
Low IgM levels may be caused by factors that can negatively impact the health of your immune system like:
- nutritional disorders
- immunosuppressant medications
- cancer treatments like chemotherapy
Some additional causes of low IgM can include:
- common variable immunodeficiency (CVID), a condition that causes low levels of antibodies
- X-linked agammaglobulinemia (XLA), a genetic condition that leads to low levels of B cells and therefore low antibody levels
- selective IgM deficiency, a condition where levels of IgM are low while the levels of other antibodies are normal
There’s also some research that suggests that IgM levels are generally lower in older adults than in younger people.
Your IgM levels can be assessed using a blood test. This involves collecting a small sample of blood, typically from a vein in your arm.
IgM levels may be measured as a part of a testing panel that looks at other types of immunoglobulins as well. Immunoglobulin G (IgG) and immunoglobulin A (IgA) are commonly included in these panels.
The symptoms of IgM that’s too high or too low can vary depending on the cause. Nevertheless, it’s always a good rule of thumb to speak with a doctor if you notice:
- frequent or recurring infections, such as sinus infections, ear infections, or pneumonia
- symptoms of anemia, such as fatigue, weakness, or shortness of breath
- easy bruising or bleeding
- unintended weight loss
- an unexplained skin rash
- bone pain
IgM is a type of antibody. It’s typically produced by plasma cells as part of the initial response to a germ or other harmful substance.
Your levels of IgM may rise above normal in the early stages of an infection. Other causes of high IgM include autoimmune diseases, some liver and kidney problems, and specific types of blood cancers and precancers.
IgM levels may decrease due to nutritional problems, certain medications and cancer treatments, and conditions that affect antibody production.
If you’re experiencing recurring infections, symptoms of anemia, or unintended weight loss, make an appointment with a doctor. They can do tests to see what’s causing your symptoms, run any needed tests, and develop an appropriate treatment plan.