Immunoglobulins

Test Overview

An immunoglobulins test is done to measure the level of immunoglobulins, also known as antibodies, in your blood.

Antibodies are substances made by the body's immune system in response to bacteria, viruses, fungus, animal dander, or cancer cells. Antibodies attach to the foreign substances so the immune system can destroy them.

Antibodies are specific to each type of foreign substance. For example, antibodies made in response to a tuberculosis infection attach only to tuberculosis bacteria. Antibodies also work in allergic reactions. Occasionally, antibodies may be made against your own tissues. This is called an autoimmune disease.

If your immune system makes low levels of antibodies, you may have a greater chance of developing repeated infections. You can be born with an immune system that makes low levels of antibodies, or your system may make low levels of antibodies in response to certain diseases, such as cancer.

The five major types of antibodies are:

• IgA. IgA antibodies are found in areas of the body such as the nose, breathing passages, digestive tract, eyes, and vagina. IgA antibodies protect body surfaces that are exposed to outside foreign substances. This type of antibody is also found in saliva, tears, and blood. A small number of people do not make IgA antibodies.
• IgG. IgG antibodies are found in all body fluids. They are the smallest and most common type of antibody. IgG antibodies are very important in fighting bacterial and viral infections. IgG antibodies are the only type of antibody that can cross the placenta during pregnancy to help protect the baby (fetus).
• IgM. IgM antibodies are the largest antibody. They are found in blood and lymph fluid and are the first type of antibody made in response to an infection. They also cause other immune system cells to destroy foreign substances.
• IgE. IgE antibodies are mostly found in tissue cells, but small amounts are also found in the blood. They cause the body to react against foreign substances such as pollen, fungus spores, and animal dander. They also protect the body from parasite infections. IgE antibody levels are often high in people with allergies.
• IgD. IgD antibodies are found on the surface of some immune cells in the body. They are uncommon and rarely found in the blood. How they work is not clear.

The levels of each type of antibody can give your doctor information about the cause of a medical problem.

Why It Is Done

A test for immunoglobulins (antibodies) in the blood is done to:

• Find certain autoimmune diseases or allergies.
• Find certain types of cancer (such as multiple myeloma or macroglobulinemia).
• See whether recurring infections are caused by a low level of immunoglobulins.
• Check the treatment for certain types of cancer affecting the bone marrow.
• Check the response to immunizations to see if you are immune to the disease.
• Check to see if you have an infection or have had it in the past.

This test may be done when the results of a blood protein electrophoresis or total blood protein test are abnormal.

How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

High values

• IgA. High levels of IgA may mean that multiple myeloma is present. Levels of IgA also get higher in some autoimmune diseases, such as rheumatoid arthritis, and in liver diseases, such as cirrhosis.
• IgG. High levels of IgG may mean a long-term (chronic) infection, such as tuberculosis, is present. Levels of IgG also get higher in IgG multiple myeloma, long-term liver disease, and systemic lupus erythematosus (SLE). In multiple myeloma, tumor cells make only one type of IgG antibody (monoclonal); the other conditions cause an increase in many types of IgG antibodies (polyclonal).
• IgM. High levels of IgM can mean macroglobulinemia, viral hepatitis, mononucleosis, rheumatoid arthritis, or a bacterial infection is present. Because IgM antibodies are the type that form when an infection occurs for the first time, high levels of IgM can mean a new infection is present. High levels of IgM in a newborn mean that the baby has an infection that started in the uterus before delivery.
• IgD. How IgD works in the immune system is not clear. A high level may mean IgD multiple myeloma is present. IgD multiple myeloma is much less common than IgA or IgG multiple myeloma.
• IgE. A high level of IgE can mean a parasite infection is present. Also, high levels of IgE often are found in people who have allergic reactions, asthma, atopic dermatitis, and some types of cancer. In rare cases, a high level of IgE may mean IgE myeloma.

Low values

• IgA. Some people are born with low or absent levels of IgA antibodies. Low levels of IgA occur in some types of leukemia, kidney damage (nephrotic syndrome), a problem with the intestines (enteropathy), and a rare inherited disease that affects muscle coordination (ataxia-telangiectasia). A low level of IgA increases the chance of developing an autoimmune disease.
• IgG. Low levels of IgG occur in macroglobulinemia. In this disease, the high levels of IgM antibodies stop the growth of cells that make IgG. Other conditions that can cause low levels of IgG include some types of leukemia and a type of kidney damage (nephrotic syndrome). In rare cases some people are born with a lack of IgG antibodies. These people are more likely to develop infections.
• IgM. Low levels of IgM occur in multiple myeloma, some types of leukemia, and in some inherited types of immune diseases.
• IgE. Low levels of IgE can occur in a rare inherited disease that affects muscle coordination (ataxia-telangiectasia).