Autoimmune Disorders

A number of different tests can help diagnose autoimmune diseases. A common feature of the tests is the detection of antibodies that react with host antigens. Such tests involve measuring the level of antibodies found in the blood. An elevated amount of antibodies indicates that a humoral immune reaction is occurring. Antibody production is, of course, a normal response of the immune system to an infection. The normal operation of the immune system must be ruled out as the cause for the increased antibody levels. A useful approach is to determine the class of antibody that is present. There are five classes of antibodies. IgG antibody is the class that is usually associated with autoimmune diseases. Unfortunately, IgG is also dominant in normal immune responses. The most useful antibody tests involve introducing the patient's antibodies to samples of his or her own tissue. If the antibodies bind to the host tissue it is diagnostic for an autoimmune disorder. Antibodies from a person without an autoimmune disorder would not react to "self" tissue. Tissues from the thyroid, stomach, liver, and kidney are used most frequently in this type of testing.