Autoantibodies are a group of antibodies (immune proteins) that mistakenly target and damage specific tissues or organs of the body. In many instances they may not be ‘pathogenic’, that is cause disease, but a sign of damage that is occurring or may be going to occur. One or more autoantibodies may be produced by a person’s immune system when it fails to distinguish between ‘self’ and ‘non-self’ proteins. Usually the immune system is able to discriminate by recognising foreign substances (‘non-self’) and ignoring the body’s own cells (‘self’), yet not overreact to non-threatening substances such as foods, dust and pollen, or beneficial microorganisms.
It creates antibodies only when it perceives what it has been exposed to as a threat (‘non-self’). When the immune system ceases to recognise one or more of the body’s normal constituents as ‘self’, it may produce autoantibodies that attack its own cells, tissues, and/or organs, causing inflammation and damage. The causes of this inappropriate action are varied and are not well understood, often resulting in a chronic autoimmune disorder.
While there is not a direct link, it is thought that many cases of autoantibody production are due to a genetic predisposition combined with an environmental trigger (such as a viral illness or a prolonged exposure to certain toxic chemicals, for example, in cigarette smoke, or benzene). Some families have been shown to have a high prevalence of autoimmune conditions, however, individual family members may have different autoimmune disorders or may never develop an autoimmune condition.
Researchers believe that there may also be a hormonal component to the cause as many of the autoimmune conditions are more common in women of childbearing age.
The type of autoimmune disorder or disease that occurs and the amount of destruction done to the body depends on which systems or organs are targeted by the autoantibodies. Disorders caused by autoantibodies that primarily affect a single organ, such as the thyroid in Graves’ disease or Hashimoto’s thyroiditis, are often the easiest to diagnose as they frequently present with organ-related symptoms.
Disorders due to systemic autoantibodies (affects multiple organs or systems) can be much more elusive.Although the associated autoimmune disorders are rare, the signs and symptoms they cause are relatively common and may include: arthritis-type joint pain, fatigue, fever, rashes, cold or allergy-type symptoms, weight loss and muscular weakness. Additional complications may include vasculitis (inflammation of blood vessels) and anaemia.
Signs and symptoms
Signs and symptoms will vary from person to person. They can vary over time and/or with organ involvement, often tapering off and then flaring up unexpectedly. To complicate the situation, some may have more than one autoantibody, have more than one autoimmune disorder, and/or have an autoimmune disorder without a detectable level of an autoantibody. This may make it difficult for the doctor to identify the prime cause and arrive at a diagnosis.
The diagnosis of autoimmune disorders starts with a complete medical history and a thorough physical examination. The doctor may request one or more diagnostic studies that will help to identify a specific disease. These studies may include:
- blood tests to detect autoantibodies, inflammation, and organ involvement/damage.
- x-rays and other imaging scans to detect changes in bones, joints, and organs.
- biopsies to look for pathologic changes in tissue specimens.
As a rule, information is required from multiple sources (rather than a single laboratory test) to accurately diagnose disorders associated with systemic autoantibodies.