Transglutaminase IgA, or tTG-IgA, is an antibody produced by the body’s immune system. It specifically targets an enzyme found naturally within the body.
Understanding Transglutaminase IgA
Transglutaminase (tTG) is an enzyme present throughout the body, playing a part in various biological processes. It helps form bonds between proteins, contributing to tissue repair and stabilizing structures. It is found in many organs, including the small intestine.
Immunoglobulin A (IgA) is a class of antibodies that forms a significant part of the immune system. These antibodies are primarily located in mucous membranes, such as those lining the digestive and respiratory tracts. IgA acts as a first line of defense, preventing germs and toxins from entering cells and clearing them from mucosal surfaces.
When these two components are combined, tTG-IgA refers to an antibody that specifically targets the tissue transglutaminase enzyme. This antibody is not normally present in high levels in healthy individuals; its presence can indicate an immune response directed at the body’s own tTG enzyme.
Its Role in Celiac Disease
In individuals with celiac disease, the immune system reacts abnormally to gluten, a protein found in wheat, barley, and rye. This reaction mistakenly identifies the body’s own tissue transglutaminase enzyme as a threat. When gluten is consumed, it triggers an immune response that leads to the production of tTG-IgA autoantibodies.
These autoantibodies result from the immune system targeting the tTG enzyme. The presence of tTG-IgA antibodies is a key indicator of this autoimmune reaction. They are produced in the small intestinal lining and can be detected in the bloodstream during gluten consumption.
The tTG enzyme modifies gluten peptides, which can enhance their ability to stimulate the immune system in genetically susceptible individuals. This process is believed to be a significant step in the development of celiac disease. Heightened levels of tTG-IgA antibodies reflect ongoing immune activity and potential damage in the small intestine.
Testing for Transglutaminase IgA
Testing for transglutaminase IgA involves a simple blood test. This test measures the level of tTG-IgA antibodies present in a person’s bloodstream. It is commonly used as an initial screening tool when celiac disease is suspected.
For accurate results, the individual must continue consuming a gluten-containing diet before the blood sample is taken. If gluten is removed, antibody levels may decrease, potentially leading to a false negative result. This test is often performed alongside a total IgA level measurement to ensure overall IgA production is normal.
Interpreting Test Results
A positive or high level of tTG-IgA antibodies typically suggests a strong likelihood of celiac disease. For individuals with moderately to strongly positive results, further evaluation, such as an intestinal biopsy, is generally recommended to confirm the diagnosis.
A negative tTG-IgA result usually indicates that celiac disease is unlikely. However, a negative result can be misleading. Some individuals have IgA deficiency, where their bodies do not produce sufficient IgA antibodies. In such cases, the tTG-IgA test may yield a false negative result, and other antibody tests, such as IgG-based tests, might be used for diagnosis.
Borderline tTG-IgA results are less definitive and may require additional testing or clinical assessment. It is also important to remember that while a positive tTG-IgA test is a strong indicator, an intestinal biopsy remains the definitive method for diagnosing celiac disease. Consulting a healthcare professional is important for accurate interpretation of results and to determine next steps in diagnosis or management.