WebMD:An immunoglobulins test is done to measure the level of immunoglobulins, also known as antibodies, in your blood. Antibodies are specific to each type of foreign substance.
The five major types of antibodies are:
QUOTE
IgA. IgA antibodies are found in areas of the body such the nose, breathing passages, digestive tract, ears, eyes, and vagina. IgA antibodies protect body surfaces that are exposed to outside foreign substances. This type of antibody is also found in saliva and tears. About 10% to 15% of the antibodies present in the body are IgA antibodies. A small number of people do not make IgA antibodies.
IgG. IgG antibodies are found in all body fluids. They are the smallest but most common antibody (75% to 80%) of all the antibodies in the body. IgG antibodies are very important in fighting bacterial and viral infections. IgG antibodies are the only type of antibody that can cross the placenta in a pregnant woman to help protect her 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. IgM antibodies are about 5% to 10% of all the antibodies in the body.
IgE. IgE antibodies are found in the lungs, skin, and mucous membranes. They cause the body to react against foreign substances such as pollen, fungus spores, and animal dander. They may occur in allergic reactions to milk, some medicines, and some poisons. IgE antibody levels are often high in people with allergies.
IgD. IgD antibodies are found in small amounts in the tissues that line the belly or chest. How they work is not clear.
The Antigliadin IgA and IgG tests have somewhat fallen out of favor due to the lack of specificity [other medical issues can be the cause of these antibodies]. However, some organizations and Doctors do feel these tests are of importance and still include them in their panel of tests. Gluten maybe an issue, and should be investigated a bit further. These tests ARE included in followup testing to determine dietary compliance, so there is value to them. The tTg spikes when there is high levels of damage to the villi, and is highly specific to celiac, so that is why doctors tend to rely on it more heavily that the others.
Hope this helps.