what is a iga blood test
What It Is. An IgA test measures the blood level of immunoglobulin A, one of the most common antibodies in the body. Antibodies are proteins made by the immune system to fight bacteria, viruses, and toxins.IgA is found in high concentrations in the body's mucous membranes, particularly the respiratory passages and gastrointestinal tract, as well as in saliva and tears. IgA also plays a role in allergic reactions.ntibodies are proteins made by the immune system to fight bacteria, viruses, and toxins. IgA is found in high concentrations in the body's mucous membranes, particularly the respiratory passages and gastrointestinal tract, as well as in saliva and tears.