Immunoglobulins are special proteins made by plasma cells, a type of white blood cell that develops from B cells. Immunoglobulins are also called antibodies. Their primary role is to protect the body by recognizing and attaching to harmful substances such as bacteria, viruses, and toxins. Once an immunoglobulin attaches to a target, it marks it for destruction, making it easier for the immune system to remove it. Immunoglobulins can also recognize and attach to abnormal or damaged cells, helping the body eliminate cells that are no longer functioning correctly.
Every immunoglobulin is made up of four connected protein chains: two heavy chains and two light chains. The heavy chains decide the overall kind of antibody. There are five different kinds of heavy chains, called A, G, D, E, and M. These give us the five main types of immunoglobulins: IgA, IgG, IgD, IgE, and IgM.
The light chains are classified into two varieties: kappa and lambda. Each antibody uses one of these. This mix-and-match system (for example, IgA kappa or IgG lambda) allows your body to make millions of unique antibodies, each designed to recognize something different.
Although your immune system can produce many different types of immunoglobulins overall, each plasma cell produces only one type. Because we all have millions of plasma cells, it is normal to find a wide variety of antibodies in the blood at any given time.
Each type of immunoglobulin has a specific role in the immune system:
IgA: Found in high amounts in mucosal surfaces such as the mouth, respiratory tract, intestines, and secretions like saliva, tears, and breast milk. IgA helps protect body surfaces exposed to the outside environment.
IgG: The most common immunoglobulin in the blood. IgG provides long-term protection after infections or vaccinations and can cross the placenta to protect newborn babies.
IgM: The first antibody made in response to an infection. IgM is very effective at destroying bacteria during early immune responses.
IgE: Involved in allergic reactions and defense against parasites. IgE levels are often higher in people with allergies or asthma.
IgD: Found in small amounts on the surface of immature B cells. It helps these cells become activated, but its role in the bloodstream is less well understood.
Immunoglobulins are sometimes measured in blood tests to look for abnormal levels. Too high or too low levels of a specific immunoglobulin can indicate an immune system issue, a chronic infection, an autoimmune disease, or a plasma cell disorder. In a tissue biopsy, pathologists may use immunohistochemistry or other specialized tests to determine the type of immunoglobulin a group of plasma cells is producing. This can help determine whether the plasma cells are normal or abnormal.
Some cancers of plasma cells make large amounts of a single, abnormal immunoglobulin. This protein, sometimes referred to as a monoclonal protein or M-protein, can be detected in the blood or urine. Examples include:
Examples of cancers that make immunoglobulins include:
Multiple myeloma: A cancer of plasma cells that usually produces a large amount of one abnormal immunoglobulin.
Plasmacytoma: A single tumor made up of abnormal plasma cells that may also produce immunoglobulin.
Waldenström macroglobulinemia: A rare type of lymphoma that produces large amounts of IgM immunoglobulin.
Finding abnormal immunoglobulins in blood, urine, or tissue samples often leads to further tests to confirm the diagnosis and determine the appropriate treatment.
What type of immunoglobulin is mentioned in my report?
Are my immunoglobulin levels normal, low, or high?
Does this result suggest an infection, an immune system problem, or plasma cell cancer?
Do I need additional blood or urine tests to measure immunoglobulins?
Will these results affect my treatment or follow-up care?