What is an Immunoglobulin?

Immunoglobulin is a type of protein that helps the body fight disease. Immunoglobulin, abbreviated at Ig, is also referred to as antibody. The substance is located in various parts of the body, depending on the type of immunoglobulin it is and its function. There are five different forms of the antibody, each with a particular job.

IgA is located in the respiratory and digestive tract, the nose, ears, eyes, and vagina. IgA is responsible for protecting the body from outside invaders. It is found in saliva, blood, and tears. IgG is the smallest form of immunoglobulin, and is located in all body fluids. It is responsible for fighting bacterial and viral infections, and is the only antibody that crosses the placenta to protect a fetus during pregnancy.

IgM is the largest antibody. It is the first responder to infection, and is located in the blood and lymph fluid. Along with mounting an initial response to foreign bodies, IgM also encourages other immune system cells to fight the infection. IgD is located in the tissues of the torso and chest, and researchers have not determined its function.

IgE is located in the various mucous membranes, in the skin, and the lungs. IgE is responsible for the body's reaction to allergens such as pollen, fungus, dander, and spores. It may also trigger allergic reactions when exposed to milk, medications, and poisons. People who suffer from allergies often have high levels of IgE.

Someone experiencing health problems may have their immunoglobulin levels tested. This is a simple blood test, and the results are typically available in a few days. It is possible for a healthcare provider to diagnose various conditions by testing antibody levels.

High levels of IgA may indicate multiple myeloma, chronic hepatitis, cirrhosis of the liver, or an autoimmune disorder such as rheumatoid arthritis. High levels of IgG are often a sign of a chronic, long-term infection, or multiple sclerosis. Elevated levels of IgM may signal mononucleosis, parasitic infection, or kidney damage. High levels of IgE indicate allergies or asthma.

Low levels of IgA or IgG may indicate leukemia or kidney damage. Low levels of IgM are often a sign of immune system problems, and low levels of IgE are often a sign of an inherited muscle condition that affects coordination. Immunoglobulin levels are very helpful when trying to pinpoint a health concern, but are not the only tests used to diagnose these conditions.