Understanding Immunoglobulin A (IgA) test
What It Is: Immunoglobulin A (IgA) is a type of antibody that plays a crucial role in the immune function of mucous membranes. It is one of the five main classes of immunoglobulins, along with IgG, IgM, IgD, and IgE. IgA is the second most prevalent antibody in the blood and is the dominant antibody in various secretions.
Why It's Important: IgA is essential for protecting mucosal surfaces from infections. It is found in high concentrations in areas of the body that are exposed to the external environment, such as the respiratory and gastrointestinal tracts. IgA helps neutralize pathogens and prevent them from entering the body.
Role of IgA:
Mucosal Immunity: IgA is the primary antibody found in mucous secretions, including saliva, tears, breast milk, and respiratory and gastrointestinal secretions. It helps protect these surfaces from infections by neutralizing pathogens.
Immune Tolerance: IgA also plays a role in maintaining immune tolerance, preventing the immune system from overreacting to harmless substances.
How IgA Works:
Production: IgA is produced by B cells (a type of white blood cell) and is then transported into mucosal secretions. In the mucosal secretions, IgA exists in a dimeric form (two IgA molecules joined together) and is known as secretory IgA (sIgA).
Circulation: In the blood, IgA is found in a monomeric form (single IgA molecule). It circulates through the bloodstream and provides systemic immune protection.
What to Expect During the Test:
Blood Sample Collection: A healthcare professional will draw a small sample of your blood, usually from a vein in your arm.
Laboratory Analysis: The sample is then sent to a lab where the level of IgA is measured.
Interpreting the Results:
Normal IgA Levels: Typically range from 70 to 400 milligrams per deciliter (mg/dL) in adults.
High IgA Levels: May indicate conditions such as chronic infections, liver disease, or autoimmune disorders.
Low IgA Levels: May suggest conditions such as selective IgA deficiency, which can lead to recurrent infections, or other immune system disorders.
Why Your Doctor Might Order This Test:
Diagnosing Immune Disorders: To check for conditions like selective IgA deficiency or other immune system disorders.
Monitoring Symptoms: If you have symptoms such as recurrent infections, chronic diarrhea, or unexplained weight loss, this test can help diagnose the underlying cause.
Evaluating Immune Function: To assess your overall immune function and response to infections.
Symptoms That Might Prompt This Test:
Recurrent infections (e.g., sinusitis, bronchitis)
Chronic diarrhea
Unexplained weight loss
Allergies
Skin rashes